Colour theory and how evolution shaped it

Colour theory describes how colours work together and how they affect our emotions and perceptions. It’s a useful field of study for artists and designers to better choose colours and combine them to convey the right messages for their projects.

But how did we evolve to perceive colour in the way we do?

You’ve probably heard about the special cells called rods and cones in the retina. Their job is to spot light and let the brain know about it. Different rods and cones react to different wavelengths, or colours, of light. When we see these colours, the cone cells process the wavelengths and tell the brain what colour we’re seeing.

Most humans are trichromats, meaning we perceive three primary colours: blue, green and red. The retina in a human eye can detect light between wavelengths of 400 and 700 nanometers, a range known as the visible spectrum.

Why dogs can’t see green

The colours we can perceive were likely shaped by factors linked to our survival. Being able to distinguish nutritious red berries against a backdrop of green probably kept our ancestors alive. Obligate carnivores, like dogs, can’t perceive green, likely because this distinction wasn’t necessary for them.

A good rule of thumb if you’re ever in a forest and want to know whether you can eat a berry is to look at how red it is. Darker reds (which, on the colour spectrum, have what we perceive as some blue or green) are usually safe for humans. Brighter reds (closer to orange) are for birds.

Later, the ability to perceive this particular colour spectrum was likely key to our our ability to farm grain. Without the ability to see when wheat had ripened and was ready to harvest, we would have been unlikely to have the idea to farm it.

The Ancient Greeks thought the sea was wine-coloured

In ancient texts, colours are described with a regularity that mirrors their appearance in nature – so lots of browns and greens, some reds and blacks, few purples or blues. Then red, ochre, green, violet, yellow and lastly, occasionally, blue. Egyptians and Byzantines had a word for blue. Ancient Greeks didn’t.

In the Iliad and the Odyssey, Homer describes the sea as being the colour of wine and the sky as bronze. Sheep also get described as wine-coloured. Honey is green.

If we don’t have a word for something, it’s possible that we (ourselves as individuals) lack a concept for it. Thus, we might not even perceive it. Interestingly, native speakers of Russian and modern Greek (who have dedicated words for lighter and darker shades of blue) can perceive a greater number of shades of blue than native speakers of English.

This is an instance of linguistic relativism – the difficulty we have retaining information from another culture or language where we lack the frame of reference from your own.

Some of us see fewer colours. Some of us see more.

And while most humans are trichromatic – with three sets of colour sensing cones, birds are tetrachromatic. But so are an undetermined number of human women.

This is the opposite end of the spectrum to the various types of colour blindness that have been identified.

It’s likely that those who are colour blind evolved that way because the colours they perceived were those that were most important to their survival and the rest simply didn’t exist in their environment or were unimportant.

Ultimately tetrachromatics are in the same boat as the colour blind – living in a world where they are the minority, a world designed for a majority whose perceptual faculties are no better or worse, simply more common.

Our perception of colour has been shaped by evolutionary and cultural factors. It’s fascinating that our language processing can affect how we experience colour. It’s not clear whether the tecnicolour world we inhabit today will affect our perception of colour in the future, or whether one day we’ll perceive a greater number of colours than we do today. Perhaps, with a bit of luck, a greater awareness of the fact that not everyone perceives colour in he same way will shape how we communicate.