Roses are red, violets are blue — but are they?

Adrian Arnold
4 min readMar 6, 2021


Do other people see the same colours as you?

Of the five recognised human senses, sight is often considered to be the most important. The loss of taste and smell while distressing is unlikely to protect you from danger while sight can alert you to situations that can threaten or enhance life. Our experience of vision starts with two basic forms of photorecepto cells in the retina at the back of the eye; rods and cones. The former have adapted to detect objects in low light and largely in black and white while the cones require brighter light to convey the photons which create over a million shades of colour in the mind.

Who is to say that what my brain tells me is “red” might not be seen by another person as “blue” in my ey and yet describes it as “red”?

This is only the start of the journey. The retinal cells have to convert their registration of a colour into an electrical signal which has to travel to the optic lobes at the back of the brain. This requires a network of brain pathways travelling along the optic nerve, through the optic chiasma, optic tracts, lateral geniculate bodies, optic radiations and visual cortex. All this activity happens at 10 million bits per second — the same speed as a computer cable connection. This allows the human eye to register up to 1000 frames per second while a 4K television only delivers 60 frames per second.

It gets more complicated when the concept of “forbidden colours” is introduced. Try to imagine reddish green — not the dull brown you get when you mix the two pigments together, but rather a colour that is somewhat like red and somewhat like green. Or, instead, try to picture yellowish blue — not green, but a hue similar to both yellow and blue.

Getting confused? That’s because, even though those colours exist, you’ve probably never seen them. Red-green and yellow-blue are the so-called “forbidden colours.” Composed of pairs of hues whose light frequencies automatically cancel each other out in the human eye, they’re supposed to be impossible to see simultaneously. The same principle applies to sound cancelling technology when certain headphones produce a cancelling frequency to background noise.

This may or may not be of interest to you but it has little to do with the question posed by this article. These electrical impulses have to be interpreted by the brain. Who is to say that what my brain tells me is “red” might not be seen by another person as “blue” in my eye and yet describes it as “red”?

We talk of people having “an eye” for colour. Artists, gardeners, interior designers and photographers all rely upon their perception of colour. Which colours go well together and those which clash are the attributes of successful artists while other people seem to possess little or no aptitude for colour matching. Is this because their brains see colours differently?

This idea is not as far-fetched as it might appear at first glance. The curvatures of both the eye and the lens within it means that the image hits the retina upside down and the brain has to learn to invert the image to reflect the true alignment. Very young babies seem to take a few days for their brains to ‘flip’ the optical image. Thus the brain has to do a lot of work ‘editing’ our visual images so it is not beyond the realms of possibility that different brains will encode colours in different ways. If I see a flower as purple and my friend registers it as green but we agree that the colour is red, why should we disagree?

Many people are living perfectly normal lives with a condition known as synaesthesia. This is a condition in which one sense is simultaneously perceived by one of the other senses. Our grandson sees numbers and letters of the alphabet in different colours and only realised recently that this was not necessarily a normal experience. There are several different types of synaesthetes. Some will ‘see’ music as colours, ‘taste’ foods as round or triangular and ‘remember’ a loved one’s image as yellow while the bully of your childhood is recalled as deep orange.

A synaesthete’s view of alphanumeric characters

The study of synaesthesia is not a modern science. It goes back to Aristotle and beyond while several well-known individuals of today share the experience. Richard Wagner, Pharrell Williams, Duke Ellington and David Hockney all have various forms of synaesthesia. Looking down the list it is almost as if the condition enhances art in its many forms.

If I see a flower as purple and my friend registers it as green but we agree that the colour is red, why should we disagree?

The problem is that we cannot, yet, get into another person’s head — but that is probably a good thing



Adrian Arnold

Retired veterinary surgeon now a collector of trivia. Married to a wonderful wife, four children and four grandchildren. Author of A Veterinary Life on Amazon.