To What Extent is Color a Physical Thing in the Physical World?

bbc | Depending on what language you speak, your eye perceives colours – and the world – differently than someone else. The human eye can physically perceive millions of colours. But we don’t all recognise these colours in the same way. 

Some people can’t see differences in colours – so called colour blindness – due to a defect or absence of the cells in the retina that are sensitive to high levels of light: the cones. But the distribution and density of these cells also varies across people with ‘normal vision’, causing us all to experience the same colour in slightly different ways. 

Besides our individual biological make up, colour perception is less about seeing what is actually out there and more about how our brain interprets colours to create something meaningful. The perception of colour mainly occurs inside our heads and so is subjective – and prone to personal experience.

Take for instance people with synaesthesia, who are able to experience the perception of colour with letters and numbers. Synaesthesia is often described as a joining of the senses – where a person can see sounds or hear colours. But the colours they hear also differ from case to case.

Another example is the classic Adelson’s checker-shadow illusion. Here, although two marked squares are exactly the same colour, our brains don’t perceive them this way.

Since the day we were born we have learnt to categorise objects, colours, emotions, and pretty much everything meaningful using language. And although our eyes can perceive thousands of colours, the way we communicate about colour – and the way we use colour in our everyday lives – means we have to carve this huge variety up into identifiable, meaningful categories.

Painters and fashion experts, for example, use colour terminology to refer to and discriminate hues and shades that to all intents and purposes may all be described with one term by a non-expert.