‘Colour is in the Mind of the Viewer’ (Elliot et al 2018)

1. Introduction

Colour, as comprising hue (red, green etc), chroma (saturation or strength of hue) and luminance (shade of dark or light), is the fundamental element and basis of all visual perception and is processed, converted and interpreted through complex physical, chemical and electrical optical systems in humans and many other species. But that is only a small part of the story. Coloured images are not simply passed through these systems as a picture to the brain but rather as series of near instantaneous electro-chemical signals for various lower and higher cognitive areas of the mind to interpret and reassemble. This paper examines colour as it relates to art and, in particular, how painting exploits various phenomena and compromises within these optical/mind processes. It begins with a very brief review of some early theories.

2. Historical Theories and Systems of Colour

Isaac Newton, (1704) identified that the colour of light was composed of many different ‘rays’ “if the Sun’s Light consisted of but one sort of Rays, there would be but one Colour in the whole World…” (ibid). He devised a useful colour wheel (Figure 1) with each colour placed in its position as it would appear in a rainbow or prism. The letters correspond to musical notes, as Newton believed (wrongly) that light behaved much like music, with similar harmonic structures.

Figure 1: Isaac Newton’s colour wheel Wikipedia Commons

In the 1800’s, von Goethe (1840), an artist/philosopher, made the important observation that perception of colour seemed to be largely to do with the viewer’s subjective interpretation rather than simply the physics of optics. He then devised a new wheel of colour (Figure 2) which included his proposed associations of colours with feelings.

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Figure 2: Goethe's symmetric colour wheel with associated symbolic qualities (Von Goethe, 1840)

The false dichotomy between the science and emotion of colour is exemplified by Judd, (1969) who, in his forward to the English translation of Goethe’s Theory of Colours, states “In view of the fact that Goethe’s explanation of colour makes no physical sense at all, one might wonder why it is considered appropriate to reissue this English translation”. (Judd, 1969:xi). But many artists have followed Goethe’s ideas of the emotional connotations of colours. For example, JMW Turner deployed (and explicitly acknowledged in his title) Goethe’s theories in Figure 3, and recent research (see 2 below) has confirmed both universal and culture-specific emotional response to certain colours.

Figure 3: JMW Turner Light and Colour (Goethe's Theory) - the Morning after the Deluge - Moses Writing the Book of Genesis exhibited 1843 (https://www.tate.org.uk/context-comment/articles/how-to-spin-the-colour-wheel)

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Around 1824, Michel-Eugène Chevreul, an eminent chemist and Director of Dyeing at the famous tapestry works in Gobelin, was puzzled by the numbers of complaints he was receiving about the lack of strength of colour in some tapestries. After considerable investigation, he discovered that the problem was not chemical, or with the dye itself, but was optical – especially in the brain’s processing of colours placed next to each other. “The want of vigour complained of in the blacks was owing to the colour next to them, and was due to the phenomena of contrast of colours” (Chevreul, 1855:xii).

In 1839, based on these investigations, he published his major work ‘De la loi du contraste simultané des couleurs’, which was subsequently published in English (Chevreul, 1855). This work included major contributions on how colours were seen, especially recognition of the viewer’s role in colour perception and, in particular, the effects on colour perception of adjacent contrasting colours. In his role as a dye chemist, he discovered ‘simultaneous contrast’ (e.g. a light grey will look darker if placed next to a lighter grey) where a perceived colour is influenced by the colours around it (interestingly this human cognitive effect also applies to contrasting sounds, personalities and so on). He also identified ‘Chevreul’s illusion’ where homogenous grey stripes of different luminescence seem to vary in shade when placed next to each other – the side next to a lighter strip looks darker. Many of his findings have been confirmed and further explored through modern neurology (see 2 below).

As well as a range of interesting and largely correct observations (although without the benefit of neurological understanding), Chevreul (1855) also produced (for the purposes of dye manufacture) a comprehensive model (see Figure 4 for simple version) of all possible combinations of colours, including the ‘third’ dimension of luminance. Previous two dimensional colour wheels had only included various categorisations of hue and saturation (e.g. Von Goethe, 1840). More recently, colour scientists such as Livingstone, (2014) have built on, and clarified the three-dimensional model (see 2 below).

Figure 4: Chevreul’s colour system in three dimensions, including luminance (z axis) – simple version (https://www.colorsystem.com/?page_id=792&lang=en )

Many artists have applied the findings of Chevreul and other colour theorists. George Seurat, for example, in Figure 5, uses colour contrast to enhance the lightness of the model’s skin by painting the wall on the left of the right-hand model’s back darker (A). Around her dark hair he has lightened the background (B). He has also enhanced the lightness of the pictures by painting a darker shade on the background (C). Where the middle model’s left leg is shown against a lighter wall, he has placed a dark line as shadow on the model’s leg (D).

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Figure 5: The Models (large version), Georges Seurat, 1887-88 http://www.webexhibits.org/colorart/index3.html

3. Recent Research into the Biology of Vision and the Psychology of Colour

“much of what has been written about colour in art is nonsense … at least in part because until recently very little was known about how the brain processes information about colour” (Livingstone, 2014:46).

In recent years, especially with advances in ‘real-time’ scanning of the brain to identify cognitive pathways, our understanding of the biology of vision, and how it impacts our perceptions of art, has dramatically increased, as summarised in Livingstone’s key work ‘Vision and Art: the Biology of Seeing’ (Livingstone, 2014).

A major finding, which reinforces and explains Chevreul’s ideas on luminance, is that mammalian brains use luminance, rather than hue or chroma, to perceive depth, three-dimensionality, movement and spatial organisation, which Livingstone (2014:44) calls the ‘Where’ system. This happens in a part of the brain, common to all mammals, separate from the part of the brain dealing with colour perception and identification, which is found in higher primates, including humans, and which Livingstone calls the ‘What’ system. From an evolutionary perspective, lower primates have evolved to be very sensitive to things that move, their position and their size, but not so much with

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D

C

B

A

who or what they are in particular. Higher primates, including humans, are also tuned to identify ‘what’ things are, including their colours and the borders in their images, based on colour changes.

The ‘Where’ system is colour-blind, with lower acuity (resolution), but is very sensitive to contrast and processes images much faster.

The ‘What’ system is colour sensitive, with higher acuity, but processes images more slowly and is less sensitive to contrast.

Colour is used for object and facial recognition (the ‘what’ system). as well as colour perception itself. Due to the complexities of this processing, and the fact that so little of it takes place within the physical eye, everyone’s experience of sights, colours and art are potentially different.

“There are indeed many people for whom the experience of red is quantifiably different from my experience of red, starting with the kind of cells in their retinas that are activated. But, because our brains are built by both genes and experience, we can also say that your experience of red differs from mine simply on the basis of knowing that our life experiences have been different” (Livingstone, 2014:33).

As far as art is concerned, the context in which one looks at an object also changes how we see it. For example, in low light humans see blue as lighter and red as dimmer, so if a painting was produced in bright light then it could look very different if subsequently viewed in low light (ibid:45)

Visual processing does not, as is often thought, present pictures to the brain. It presents electrical/chemical information which the brain translates and interprets. There are numerous opportunities along this process for individual differences and, indeed, errors (see Sacks', 1998 for numerous examples). This processing is mirrored in some ways by computer handling of images – for example, our receptors respond more to small areas of light which means the brain processes discontinuities in light, rather than encoding whole areas with the same densities. This requires less energy and connections within the brain. This method of encoding changes in colour, rather than areas of the same colour, is also the basis for image compression in computer processing.

The complexities and evolutionary compromises of the physical and cognitive visual system leads to many other illusions and effects which are not present in the original image. These phenomena can be used by artists (as with Seurat’s use of the simultaneous contrast effect noted above).

The Herman Grid (Figure 6), where the eye sees small grey dots at each intersection, despite the fact they are not actually there, is another example of a simultaneous contrast illusion.

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Figure 6: The Hermann Grid. (Thomson, G. and Macpherson, 2018). https://www.illusionsindex.org/i/hermann-grid

Similarly, we interpret, for example, black type on a white page exactly the same ,even if part of the page is in shadow and actually darker than the black in the illuminated area, and in the Cornsweet illusion (Figure 7 and Gert, 2015) the left hand oblong looks darker but is in fact the same colour as the right. The illusion is caused by a small areas of dark (left) and light (right) in the middle. If you cover the middle section, then both sides will be the same shade.

Figure 7: The Cornsweet Illusion. https://www.tandfonline.com/doi/abs/10.1080/00048402.2014.1001414?casa_token=Kbrm6-SbZt4AAAAA:dpQOb7tqHyCDNJ49MACEfJy9rTusZ3wCgNdjJyZXZIMA3WkiXeVcclQMKr_LwxVrarxf3J8waDg

Geier & Hudak (2011) showed that this effect was not due, as was previously thought, to physical properties of the retina, but to the brain’s translation and interpretation of the optical signal. In Geier & Hudák’s experiment, a progression of dark to light stripes (a ‘Chevreul staircase’) was placed above a progression of light to dark stripes (Figure 8).

Figure 8. The effect of a luminance ramp background.

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They were both placed on a background shaded from light to dark (a luminance ramp). The placement on this background has significantly changed the illusion. Where the progression of the staircase is opposite to that of the ramp (i.e. the upper staircase) then the illusion is cancelled out, but where the progression of the ramp and of the staircase are identical (lower staircase) then the illusion is much stronger (Geier & Hudák, 2011).

Artists can use this processing effect. By “introducing gradual changes in background luminescence, the artist can induce opposite apparent shifts in the luminescence of the foreground, which adds to the perceived luminescence of the foreground” Livingstone (2014:61). Line drawings, also, are seen as correct representations of the bordered shapes between colours or lightness, even though such lines rarely exist in actuality.

As information is processed through increasingly complex levels of the brain, so the neurons seem to have evolved to select for things like orientation and even, at a high level, to features such as faces.

As well as illusions which are shared by most people, brain injuries can cause specific effects which, until recent advances in scanning, were the only way to explore which processes occurred where in the brain. For example, people with strokes can retain fully functioning ‘where’ processes but with no ‘what’. In one case, a man could accurately draw a teabag, ring and watch, but had no idea what they were – he was functionally blind (Farah, 1990).

Similarly, (Sacks, 1998) reports on an artist who, after a brain injury to the temporal lobe, lost all colour perception (even when dreaming!) but was still able to see and recognise objects in greyscale. Again, slightly different injuries result in people not being able to recognise familiar people or their gender, even though they can recognise features such as nose, eyes etc. Another person wrote to Sacks (ibid) saying that since losing his colour sense, his vision had become ‘like an eagle’s’. This could be explained by the exclusive reliance on the ‘where’ system, with its much greater acuity. People with damage to their ‘where’ system, on the other hand, cannot, for example, judge where things are or whether they are moving (Livingstone, 2014:61) seeing poured fluid, for example, as frozen in time.

In art, the use of equiluminance is equivalent to turning off the ‘where’ system, as there is no difference in luminance between the differently coloured objects in the picture. The object can be seen and identified by its colours, but its position will feel ambiguous and it will look flat. In art, equiluminant colours can cause a sense of vibration, motion or odddness. Its difficult to achieve equiluminance (indeed it is difficult for people/artists to judge the relative luminance of colours) but Anuszkiewicz (Figure 9) painted several works specifically exploring these concepts.

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Figure 9: Richard Joseph Anuszkiewicz (1960) Plus Reversed (a study of colour http://collection.blantonmuseum.org/Obj14578?sid=1742&x=5265460&port=131

High contrast next to equiluminance can induce a sense of movement. In Figure 10, for example, the red and blue areas of equiluminance seem to flow because they are placed next to areas of high contrast.

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Figure 10: Isia Leviant (1984) Enigma, https://arstechnica.com/science/2008/09/an-enigma-solved/

Artists, especially the Impressionists, use the technique of equiluminance to blur outlines and suggest motion (Livingstone & Zeki 2014). The sun, in Monet’s ‘Impression Sunrise’ (Figure 11) is painted with the same level of luminance as the sky and clouds (as can be seen on the right-hand version converted to grey-scale). This makes the sun’s position more ambiguous and vibrant than if the sun were rendered more traditionally and brighter in the picture.

Figure 11: Monet 1873. Impression Sunrise http://www.webexhibits.org/colorart/monet.html

Monet produces the same kind of effect by painting the poppies in Figure 12 with the same luminance as the field.

Figure 12: Monet, 1873. Poppies, Near Argenteuil

Another interesting feature of the human visual system is that acuity is more pronounced in the central (foveal) field of a gaze. So, the eye can be encouraged to move around a picture or change the impression of areas by painting different areas in more or less blurred or detailed style. Livingstone, (2014:71) suggests that Leonardo Da Vinci deliberately deployed this affect by making the Mona Lisa’s mouth blurred (sfumato) with the ‘smile’ suggested in the coarser components, so that when looked at through peripheral vision she appears to smile, whereas through foveal vision it is less clear – making her expression ambiguous and mysterious. Livingstone suggests that, artistically, blurred features are more functional in suggesting emotional states as we tend to assess mood by looking quickly, without focus, at people’s whole faces (i.e. not using foveal vision to focus). Eyes are then drawn to areas of detail, high contrast and human features, particularly eyes (Yarbus,

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1967). Renoir (Figure 13), for example, draws our attention to the face by making the features high contrast and very detailed compared to the low resolution of the rest of the picture.

Figure 13: Pierre-Auguste Renoir. 1876. Madame Henriot. https://www.google.co.uk/search?q=renoir+madame+henriot&rlz=1C1PRFI_enGB740GB747&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjf7Pz09LfdAhXJK8AKHTdwBNoQ_AUICigB&biw=942&bih=583&dpr=2#imgrc=XMmfAjCz3OsukM:

This peripheral imprecision is used effectively in Impressionist painting because the visual system interprets the less focused image to complete the picture itself. Similarly, impressionism gives movement through equiluminance but also because the level of detail is compatible with the brain’s experience of transience. As instanced by Livingstone (2014:76 ), Monet’s ‘Rue Montorgueil’ (Figure 14) seems full of movement compared to Poussin’s ‘The Abduction of the Sabine women’ (Figure 15), despite the latter subject being innately more dynamic. Impressionists are reproducing the effect of what the brain interprets from a single glance at a moving scene.

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Figure 14: Claude Monet. 1878. La Rue Montorgueil. https://thesquirrelreview.com/2015/01/13/la-rue-montorgueil-by-claude-monet-1878/.

Figure 15: Poussin 1634. The Abduction of the Sabine Women. https://commons.wikimedia.org/wiki/File:Nicolas_Poussin_-_The_Rape_of_the_Sabine_Women_-_WGA18296.jpg.

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The Monet (Figure 14) also demonstrates another effect, ‘illusory conjunction’, where the mind combines the features of two images into one and reassigns a colour or shape, if presented peripherally or transiently. In the Monet, the flags give an impression of the French tricolour, even though many of them are actually completed in only one colour.

Similarly, Cubists might be resonating with higher functions of the ‘What’ system which responds to specific objects (like facial features, which appear to trigger specific high-level neurons) from any viewing angle (Figure 16). Basically, engaging the ‘What’ system and disengaging the ‘where’.

Figure 16. Picasso 1937 Weeping Woman. https://peda.net/jao/lyseo/opiskelu2/ojkuo/tjt/kuvataide/kkjk/arkisto-2016-2017/kkjksjj/muotokuvia-omakuvia/muotokuvia-omakuvia/ppww12

In the retina, the three cone signals are converted into two-colour opponent signals, where the levels of different cone classes are compared by subtraction and a luminance signal that is the total activity added from all three cones. The other way would be to simply pass along the levels of activity in the three cone types (equivalent to x, y, z axis in 3D imaging). Colour opponent method has developed through evolution in higher mammals as an addition to the simpler luminance (grey-scale) process. The ‘where’ system uses almost entirely the luminance dimension, whereas the ‘what’ system uses both the summed cone data and the subtracted cone inputs. Seurat used this grey-scale contrast approach to great effect in Figure 17, where the background is much lighter on the left to accentuate the darker side of the figure and vice versa.

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Figure 17: Seurat (1881) The Black Knot (photographed from (Livingstone, 2014:123)

Because of colour opponent coding, red and green light cancel each other out (leaving white) as do blue and yellow), so some colours that have peaks in both red and green look the same as colours that have neither (e.g. cobalt blue vs ultramarine). Colours (of light) that that neutralise each other when mixed, enhance each other when adjacent. We also see opponent coloured after-images e.g. staring at a red spot leaves a cyan afterimage, blue leaves yellow and so on (Livingstone, 2014:92).

Artists have long portrayed the effects of light, for which the visual system utilises the luminance (‘where’), not colours (‘what’). Our natural environment means we expect light from above – so, generally, a thing bulging out would be lighter at the top. A thing dented inward will be darker at the top and colours with similar luminance, even if distinct hues, will not suggest depth.

It is very difficult for artists (and everyone) to consciously judge the relative luminance of hues, especially in view of salience – where hues that are rare in a scene tend to jump out and look brighter (e.g. red blobs).

Da Vinci (and MacCurdy, 1939), for example, made his figures and clothes generally mid-tone so that he could use darker and lighter for more extreme highlights.

“Hence I would remind you, O Painter! to dress your figures in the lightest colours you can, since, if you put them in dark colours, they will be in too slight relief and inconspicuous from a distance. And the reason is that the shadows of all objects are dark. And if you make a dress dark there is little variety in the lights and shadows, while in light colours there are many grades”. (Da Vinci & MacCurdy, 1939:286).

Henri Matisse discovered that he could use unrealistic hues (to convey emotion) and still give an appropriate sense of depth and shape, as long as the relative luminance was appropriate (e.g. Figure18).

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Figure 18: Henri Matisse 1905 La Femme au Chapeau https://www.henrimatisse.org/woman-with-a-hat.jsp

As noted above, the colour perception part of the ‘what’ system has a much lower resolution than the ‘where’ system. So, a coloured shape will be seen as conforming to an outline even if in reality it does not. Hence artists often use ink line to delineate a shape with its colour very imprecisely laid down (Figure 19).

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Figure 19: Karen Gilmour 2018 Line and Wash https://karengillmoreart.com/2014/02/22/technique-of-the-week-combining-pen-ink-and-watercolour/

The brain will see the same colour across a surface (surround antagonism) even if the luminance changes dramatically, because we are more sensitive to edges and clear changes in hue. As described above, like computer compression, we basically have to process less information. When a dark chromatic contour (e.g. purple) surrounds a lighter chromatic contour (e.g., yellow), the lighter colour will assimilate over the entire enclosed area. This is known as ‘the watercolour effect’. In Figure 20, for example, the small yellow margin seems to spread up to the next clear border, whereas, in reality, the internal areas (except for the small margin of yellow) are exactly the same white as the outside.

Figure 20: The watercolour Effect (Pinna, Brelstaff, & Spillmann, 2001)

Our perception of the colour of an area therefore depends mainly on what we see at its edges.

This effect is used in the work of Pointillist artists, for example Seurat (Figure 21), where the eye can see the both the individual dots and their blending together to form a colour at the same time. In

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this case, the size of the dots is crucial (Livingstone, 2014:176). Too small and the eye would only see the overall hue, too large and the eye would only see the dots. The visual system also blends the colours if they are seen as being part of the same surface (i.e. between two higher contrast borders). So the water is seen as a homogenous expanses of the same surface, despite the different hues, chromas and luminance within the shape.

Figure 21: Georges Seurat, 1884. Bathers at Asnières (Une Baignade, Asnières).

Seurat also invokes Chevreul’s notion of simultaneous contrast, where the light hue of the right sides of two right hand boys is enhanced by a darkened blue luminance of the water whereas where the boys are in shade the water blue is lighter. The dark face of the central seated boy is, for example, surrounded by a lighter shade.

More recently, the technique of photo-montage (Figure 22) has used a variation of pointillism to create an overall image from thousands of smaller images whose detail can only be discerned on close inspection.

Figure 22: Robert Silvers, 2008. Photo Mosaic of Girl with the Pearl Earring, detail, 2008. with detail on right. http://www.photomosaic.com/portfolio.html

Interestingly, although the receptors for various senses differ widely (e.g. the mechanical cochlea for sound vs the chemical cones of the eye), the brain processes the input signals in remarkably similar ways, to such as extent that when the optic nerves of guinea pigs were re-routed to their auditory

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cortex, their visual sense still functioned adequately (Budinger et al 2006). This is one explanation for synaesthesia – where people ‘see’ sounds or ‘hear’ colours – the particular part of the brain has received signals from the wrong sensor. Often people associate colours with numbers and this is because the relevant parts of the brain are very close to each other. Even people without synaesthesia can sometimes vaguely relate, say, a taste to a feeling (e.g. cheese as ‘sharp) or a colour to a sound or a smell to a colour. This ‘capability’ is a range rather than either on or off, so everyone has the sensation to some, mostly very slight, degree. Not surprising then that people experience strong emotional feelings from music, colours or tastes.

Dyslexics may experience text as being equiluminant – they often describe words as jumping around. But also, our parietal lobe smooths out the images from our constantly moving eyes which might not occur in dyslexics, who may struggle with ‘fast’ perception but be better at ‘slow’ perception – which produces great sensory accuracy. Similarly, those with poor depth perception may be able to produce better 2d representations of the 3D world (Livingstone, 2014), because they see the 3D world as it is represented on a 2D plane extremely accurately. The artist Chuck Close, for example, who uses pointillism as in Figure 23, has various neurological conditions: “I have trouble recognising faces, particularly in three dimensions … I do have a photographic memory for things that are flat … almost every decision I’ve made as an artist is an outcome of my particular learning disorders.“ (Yuskavage, 2011)

Figure 23: Chuck Close 2012. Self Portrait (screen print). https://www.artsy.net/artist/chuck-close.

4. Colour and feelings.

Colour psychology as a science, has been significantly enhanced by recent advances in imaging technology. Subjects such as colour harmony, colour preference and the emotional impact of colour have long been the subject of speculation but now can be explored with more rigour. This is not to say that the artists themselves should follow science blindly – artistic sensibilities and ideas should

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prevail – but knowledge of colour psychology is a useful tool. Following various explanations of the structure of colour and its processing (e.g. Chevreul, 1855; von Goethe, 1840), others proposed emotional impacts or preferences for various colours. Early theorists such as Newton, (1704) had proposed, for example, that there was a natural harmony between certain colours, analogous to musical chords. However, empirical studies do not always support these early ideas (Whitfield & Whelton, 2015:100).

“Colour is a highly complex perceptual experience that is an integrative product of numerous characteristics of the physical stimulus, the observer, and the environmental surround.” (Elliot et al., 2018:3)

Colour science sees the psychology of colour as being impacted at all stages of processing: light stimulus, retina, subcortical structures, cortex, image, which range through physical, physiological, psychophysical and psychological. All of these stages are themselves impacted by higher order psychologies of gender, culture, development, expectations and experiences.

“not only can colour perception influence affect, cognition, and action, but also the psychological state of the observer can influence the way in which the basic mechanisms of the eye process light stimuli” (Elliot et al., 2018:4).

Within the science of colour psychology are various subject areas including:

Colour preference Perceptions of colour harmony Colour emotional impact and symbolism, tradition and folklore (e.g. white as good, black as bad,

red as scary), camouflage, warning signals, emotional responses, colour as metaphor Colour vision differences ( which can be impacted by aging, processing deficiencies etc) Influences of colour on biological and psychological functioning – attention, mating,

performance, perception, Phenomena such as visual illusions and synaesthesia (which we have discussed above).

Here we will briefly explore the first three topics as they relate to the practice of art.

Colour Preference

It has been suggested that there are universal preferences, or ‘likes’, for certain colours such as blue. (Eysenck, 1941), for example, carried out a meta-analysis which suggested that blue was the most preferred colour and yellow the least. Subsequent studies found that different cultures had different results, that the preference was highly influenced by both luminance and saturation (the ‘right’ yellow was preferred over the ‘wrong’ blue) and there was a wide variation between people. Colour psychology required a three-dimensional specification of colour including luminance, as described by Chevreul, (1855) and more recently by Livingstone, (2014). Studies, particularly by the Berkeley Color Project, have demonstrated that colour preferences vary between individuals but also when those individuals are in different situations (Racey, Franklin, & Bird, 2018). However, even though individuals vary in their preferences, colours such as blue are the most commonly liked and yellowy-green the most commonly disliked. In addition, preference rises steadily as hues get bluer and less yellow, and lightness and saturation also have an impact (e.g., saturated yellow is preferred over dark yellow (Palmer, Schloss, & Sammartino, 2013)

Racey and colleagues (2018), at the Sussex Psychology Department Colour Group, used MRI scanning to demonstrate that brain activity is modulated by colour preferences, even when such preferences

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are irrelevant to the ongoing task. The area of the brain that dealt with colour preferences was similar to that which deals with other types of preference.

Harmony

Harmony between two or more colours is, of course, a different concept than preference for an individual colour and colour psychologists have made some interesting discoveries, for example, that ”Preference for harmony decreases with artistic training.” (Ikeda et al 2015:3). The main quest has been to identify the key principles which would lead to colours being seen as harmonious – universally or by particular groups of people.

Early theorists had suggested (MacEvoy, 2015) that:

Colours having complementary hues tend to appear harmonious Colours having the same hue tend to appear harmonious Colours having the same chroma tend to appear harmonious Colours having the same lightness tend to appear harmonious

Ou & Luo, (2006) identified several key principles (as illustrated in Figure 24):

“Equal-hue and equal-chroma. Any two colours varying only in lightness tend to appear harmonious when combined together.

High lightness. The higher the lightness value of each constituent colour in a colour pair, the more likely it is that they appear harmonious.

Unequal lightness values. Small lightness variations between the constituent colours in a colour pair may reduce the harmony of that pair.

Hue effect. Among various hues, blue is the one most likely to create harmony in a two-colour combination; red is the least likely to do so. In addition, bright yellows more often create harmony in two-colour combinations than dark yellows (i.e. khaki colours).”

Figure 24: A graphical representation of colour harmony in CIELAB colour space (L. Ou & Luo, 2006)

Suppose we are looking for a colour to be combined with cyan in order to generate a harmonious pair. As shown in Figure 24, cyan is located on the equiluminant plane at a certain point. “According to principle (1) above, the colours lying on the vertical line that goes through this cyan colour (i.e., the line containing the blue and the red arrows) are most likely to create harmony when combined with this cyan. According to principle (2), the colours located in the direction of the blue arrow are better choices than those following the red arrow. According to principle (3), the colours within the

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range of the yellow arrows should be avoided as they are too close to the example cyan colour. Thus, colours on the line of the blue arrow and above the yellow-arrow region are the preferred solutions. Note that principle (4) is not used in this example, as it applies only when a colour-pair comparison is made between different dominant hues.” (Ou & Luo, 2006)

Szabó, Csuti, & Schanda, (2009) found similar results: As lightness difference increased, then the colour harmony score also increased. The highest colour harmony scores were produced by colours having small differences in chroma. Higher lightness overall resulted in a higher harmony score.

Of course, there are key differences between mixing light and mixing paint. Paint mixing is subtractive where we mix the absorbent pigments, subtracting their light reflectance rather than adding light reflectance. In paint, the primaries are Cyan, Magenta and Yellow as, for example, Cyan is minus the red absorbing pigment. Similarly, in light, blue added to yellow results in white, whereas in in paint, Blue mixed with yellow (subtracted) results in green.

Colour emotional impact and symbolism

Colour in emotion can either be received (as in Chinese seeing the colour red as causing happiness) or as a messenger e.g. red seen as making something warm, exciting. There is a strong relationship between colour and affective response. Many of these responses appear to be universal - “A colour at a hue angle in the red-orange region tends to be regarded as a warm colour; the more saturated this reddish colour appears, the warmer feelings the colour tends to elicit. On the other hand, a bluish colour tends to be regarded as cool; the more saturated this bluish colour appears, the cooler the colour tends to feel.” (Ou, 2018:401). Ou (ibid) used EEG and skin conductance (as signals of emotion responses) and found stronger responses to red light than to blue, green or white. He identifies three dimensions impacting feeling and emotion:

Hue – where red/orange hues feel warm while blue feels cool. Luminance – where higher luminance tends to feel soft and light, with lower luminance feeling

hard and heavy. Chroma- Higher saturated colours feel dynamic, clear and active with a strong impact on the

observer, whereas desaturated colours feel calmer, ambiguous and less active.

Ou (ibid) found very little cultural difference between Western and Chinese observers’ responses for warm/cool, heavy/light, and active/passive. But he found higher differences in colour preference - like/dislike between cultures, professions, gender and so on. For example, females preferred lighter colours more than men and people with design backgrounds liked colours similar in hue, more than those with non-design backgrounds.

Artists certainly use these principles, often to create conflicting emotions. Mona Hatoum for example (Figure 25), has used warm hues and high luminance in the centre of the picture so the viewer starts off with a warm feeling but as the eye moves out, the sense becomes more violent.

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Figure 25: Mona Hatoum, Light at the End, 2002

Similarly, in Figure 26, the ‘friendly’ primary hgh chroma colours work in contrast with the unfriendly nature of the cage itself.

Figure 26: The Mexican Cage, Mona Hatoum, 2002.

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Tantanatewin & Inkarojrit, (2018) investigated emotional responses to various colours being used in restaurant decoration (simulated on a PC). Their results suggested that the use of warm tone and high-value colours (e.g. light-pink, cream, orange), induced a positive perception of the environment and increased the probability of entering the restaurant. The use of cool-tones and low-value colours (e.g. blue and dark-grey) induced a negative perception of the environment and decreased the probability of entering a restaurant.

Researchers have also experimented with the use of colour to focus attention. Elliot et al., (2018:496) found that “the trichromatic visual system itself is optimally tuned to discriminate fruit and young leaves from natural backgrounds, as well as changes in skin appearance associated with changes in blood flow, the fastest response times [attention] were for targets whose chromatic loci were close to that of lips and skin.” They also found that people tend to focus on things of the same colour as something recent that was of interest, which highlights the relatively unexplored dimension of time and recency in exploring colour psychology.

Research has also found that colour meaning or symbolism is not generally universal. Monochromatic hues are symbolic for funerals in China (white clothes), and the UK (black clothes and white flowers) but colourful clothes are common in Africa for example. Folk history often defines colour associations. For example, green is seen as unlucky in Scotland based on the colour of the tartans of defeated Scots in a famous battle whereas green seen as the national colour of Ireland derives from the green flag and green being seen as lucky in the Middle East arises from the blooming of the desert after rains. However, in general, white or lightness is more often positive whereas black or darkness is more often negative. The main symbolic colours – black, white and red – are often seen as representing darkness, light and blood but might also have derived meaning because they were relatively easy to produce in prehistoric times and therefore have a long tradition of association. Interestingly, in language development, the words for black and white typically appear first, followed by red and then words for the other hues (Hutchins, 2018:351)

In the UK and other related cultures, such as the US, black and white are often used to describe good and bad, respectively (e.g., a “dark day” or a “bright time”). Red is typically used to describe emotions such as anger (e.g., “seeing red”), while green is sometimes used to convey envy; yellow, cowardice; and blue, sadness. Experiments in the UK have found that darker uniforms caused the wearer to act more harshly (giving more penalties) as well as behaving more aggressively. People in dimly lit rooms tended to cheat more! An angry face on a red background was recognised as angry more quickly. A happy face on a red background was recognised as happy less quickly. People were more likely to honk a red car. Depressed people saw less difference between black and white i.e. saw things as grey. (Meier, 2016:422)

5. Conclusion

Artists have long exploited humans’ complex processing of hue, chroma and luminance to create effects, illusions and emotions int heir work. In painting, in particular, several art movements utilise a particular phenomenon, such as equiluminance as used by impressionists and watercolour effect as used by pointillists. Many great works deployed a range of techniques to great effect without any knowledge of the underlying colour psychology but based on deep thought and experience of the effects of colour. Artists will continue to lead in experimenting with new ways of creating emotion and impression – with science following on to explain the underlying rationale. And yet, it still feels like human creativity/invention and feeling will be the key ingredient for producing art (for humans), even as colour psychology, visual processes and resulting techniques and rationales become better

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understood. For some forms of art, such as graphics and commercial art, it may be that the artist will become a technician/craftsperson, applying well understood science to the creation of images. Also, as in many fields, there is potential for technology to carry out activities currently requiring human capabilities. Robot art is already a well-established field, and as knowledge and understanding of colour psychology increases and AI capabilities develop, more and more of what is currently produced by artists may well become technology-based. But where (as I have previously argued) the art requires an intention by a human to convey an interpretation of a feeling or situation, then evocative and moving art will still be produced by people with unique creative capabilities – ever-stretching the boundaries and understanding of art, vision and psychology.

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