What makes some colour combinations look good?
The answer lies in the neurophysiological basis of colour vision.
Light entering through the pupil falls on the retina at the back of the eye. The multi-layered retina includes photoreceptors which translate light into neural impulses and other cells which begin the process of combining and interpreting those impulses into objects. This processing continues as the optic nerves & tracts weave through the brain to the visual cortex and is eventually completed as data in visual cortex is interpreted consciously and unconsciously by the rest of the brain.
These final processes mean that we can “learn” to appreciate certain colour combinations and is why we associate certain colour combinations with certain events (for example, red & green at Christmas or pastel pink & blue for Easter). These culturally acquired associations can be so powerful as to overwhelm any other underlying basis of colour harmony.
In the absence of a strong prior assocation, certain colour combinations will still please us more than others, because of our neurophysiology.
We have two types of photoreceptor: cones and rods. Cones predominantly exist in three types, each most sensitive to a particular set of light frequencies. This is the Trichromatic Theory of vision. The graph shows the sensitivity of different receptors to light:
Colloquially, they’re called blue, green and red photoreceptors but the graph shows that in reality the wavelengths are not so discrete. The blue is almost indigo/ultramarine, the green is a vegetal shade, and the red is muddied with yellow. This blurring is why the cones are more technically named by the S(hort), M(edium) and L(ong) wavelengths they’re most sensitive to. Evolutionary biologists have plenty of theories for why we should develop sensitivities to these colours; you can probably extrapolate some yourself, based on those peak colours and what exists in the natural world.
Our photoreceptor sensitivities account for the 3 additive primary colours of red, green and blue. They are drawn from sufficiently separate parts of the visual spectrum to be used to create any new colour, as this image demonstrates (the circles at the corners of triangle are the primary colours used in the sRGB monitor system):
While our photoreceptors transduce light in these sets of wavelengths, the neural impulses they generate are recombined during visual processing to create cognitive effects influencing how we perceive colour combinations, enabling us to perceive more complex colours and determine how they look against each other. This begins in other layers of the retina. Neural impulses proceed through bipolar cells to ganglion cells. Ganglion cells are not sensitive to one colour but to pairs of colours. One colour lets ganglion cells continue firing, the other stops firing. The two key types of ganglion cell are red/green and yellow/blue. We’re hard-wired to see in this Colour Opponency. We cannot see a “reddish green” or a “yellowish blue” (at least not without carrying out a very tightly-constrained experiment that makes some see “impossible” colours they can’t verbally describe). In fact, if you stare at a red square for a while, and then stare at a white wall, you’ll sometimes see an illusory green square, the afterimage being its opponent colour.
At this point, artists will point out that they use different primary colours. These are the subtractive primaries, forming the basis of the artist’s colour wheel (as explained on this art blog). It’s a hugely important device when mixing colours to make new shades, but doesn’t govern visual perception, which is based on the psychological and additive primaries. Having said that, because 2 primaries (red & blue) are the same across systems, and the position of the third primary on the colour wheel (yellow) is not far from psychological primary green, the artist’s colour wheel can still be used – with some caution – to determine what colours go well together. However, an RBG wheel can work better than the RBY one for this purpose. An RBG wheel (or star) is below:
Trichromacy and colour opponency mean that primary colours appear highly contrasting and vivid against each other. Using Red, Blue & Green together creates a bold and simple colour scheme. Because of cultural associations, it can remind us of childhood toys and naive innocence but it can also seem gauche and garish to adult eyes. Move one notch around the wheel and imagine an outfit of, say, Orange, Violet & Spring Green. Highly contrasting again, with the same risk of garishness and without the redeeming childhood association. More Halloween than anything else, perhaps. Move around again, and use Yellow, Cyan & Magenta… well, the point is clear!
Let’s try something different. Imagine an outfit consisting of some colours close to each other and one almost directly opposite each other. e.g. navy suit with paler blue shirt and yellow or orange tie. Suddenly the effect is pleasantly vibrant. This vibrancy arises because colours appear brighter when laid against their complementary colours due to a neurophysiological principle called Lateral Inhibition. Lateral inhibition suppresses neural activity from nearby cells. So if you have a yellow tie against a navy suit, you get an enhancement of the differential effect of the photoreceptors on the blue/yellow ganglion cells. Put simply, the colours brighten each other.
For an evening outfit, try picking colours all drawn from the same side of wheel e.g. keep the navy suit and pale blue shirt but swap in a dark purple tie. The more eccentric might even use a dusky pink shirt. Either way, there’s little lateral inhibition, so colours appear darker and richer, adding a touch of luxury and decadence to the outfit.
White and black also work through lateral inhibition on the colours around them. They enhance contrasts, appearing to deepen already dark colours and lift lighter colours. While our cultural associations traditionally associate black with night and white with day, because both in fact work quite similarly, black can be used to great effect in daytime outfits (see Princess Eugenie’s recent Royal Ascot teal/black outfit) and white can do the same at night (as in the gloves of this vintage Dior outfit or the shawl in this Chanel one).
The neurophysiology of vision is the basis of our colour perception. Use it to you advantage, to understand why you like an outfit, and to create new ones.
(Inline images in this post are public domain, from Wikimedia Commons)