Are gees bees?

Messing about with paint as children we learnt that the primary colours are red-blue-yellow. That was a good lesson which gave me years of use. Growing up, playing with lights on stage, I found the limits of that understanding. What I’d learnt was true of paints, which is subtractive colour. When you deal with lights, additive colour, the primaries are red-green-blue. Thinking with this has advantages in today’s world, where the use of pigments is less widespread than the light that comes from screens and LED bulbs. But all the theory that springs from this simple fact seems to miss one interesting point: colours are a human construct.

Yes. Colours are produced in our bodies. Some neurons have a specialized function which allows them to respond to light. These are called photo-receptor cells. Some receptors work in low light, and only distinguish levels of brightness. That’s why the expression “All cats are grey in the dark” brings a sense of recognition. Others work when the light is brighter, and give us a sense of colour. Most humans have receptors for what we call the red, green, and blue colours, and only for these. Once we understand this physiology of colours, we begin to understand the underlying neurodivergence due to which some people see only two primary colours.

This leads me to think about colour perception in other animals. It seems that many others have, and most of my questions are simply answered by reading. It turns out that all vertebrates have colour receptors (things like starfish can sense light and dark, but don’t have eyes). Our closest relatives, chimpanzees, orangutans, and gorillas see three primary colours. Most monkeys seem to have two kinds of colour receptors, meaning they would see in two primary colours. Several species of fish see the world in three primary colours. Four kinds of colour receptors have evolved in multiple lineages of birds (I’m sure they see through all the camouflage that dedicated birders wear). The record holders are mantis shrimps with 16 classes of colour receptors, and bluebottle butterflies (Graphium sarpedon) with 15 distinct types of colour receptors.

Can you imagine seeing with 16 primary colours? I would have brain overload every time I opened my eyes. It is not possible for me to imagine the world as these creatures see it. For example, would birds see different shades of colour in what we think of as uniform matte black? Since birds evolved from dinosaurs this raises the question about whether these ancestral birds also could see also the world with four primary colours. Ancestral mammals were nocturnal, and would probably have seen the world only in shades of gray. I doubt they would have won over the world if a little asteroid had not intervened. And what about murky seabeds? They must seem to be a riot of colour to creatures which evolved there.

Click to expand

If the colours that we see are such a human thing, then how uniform is our perception of a colour? Different human languages contain a different number of words for colour. Almost all have names for white, black, and red. So, no matter which culture you belong to, unless one of us is neurodivergent, I think we would agree about the gallery of reds. However, some languages do not have separate words for blue and green. That indicates that there may be scope for confusion between these two colours.

I invite you to take part in an experiment with the gallery above. I’ve selected photos in which there could be areas of blue-green ambiguity (in the second from last photo, for example, I see one plastic stool which is a dark blue, one which most viewers agree is a shade of green, and one, right in front, which some call blue, and others, green). I’ve arranged the photos such that to my eyes the most ambiguous areas go from being clearly green to clearly blue. Do you agree with this ordering? More, I see the first 13 photos as containing clearly green hues, sometimes bordering blues, but not crossing the line into a true blue. The last of these is the piece of jewelry with a bluish-green jade turquoise and coral. In the 14th photo, parts of the salad leaves distinctly appear blue to me. It will be interesting to see your replies.

A vision of colour

What is a garden all about? I take a stroll in a garden now and then when I have to sort out a knotty problem. The Family enjoys a walk in a garden because she meets people there, some old friends, some people whom she doesn’t know more than to nod at. My mother would spend time in her garden picking up dry leaves, digging at beds, and arguing with the gardener who would come by to help her. And then there are times when I take my camera on a walk to photograph flowers and bees. And I always wonder whether the bee sees what I see.

What is colour? There has been a century long dispute about this among philosophers. Before you dismiss it as just another meaningless dispute, think about this. Would a flower be any different if my brain was rewired somehow so that I saw the colours in the image on the right where every other human saw that in the left hand image? Certainly not. I can run this experiment by leaving a camera to take images by itself and display it to me on a screen in a room, but invert the colours before showing me the photos. In a while I would learn the colours of the different flowers, and those of the honeybees which visit them. My recognition of the object is not tied to its colour. We consciously use this notion when we use colour codes, or show images in false colour. But, as the experiment shows, all the time, in everything that we see, colour is an arbitrary label which we put on the world.

If colour does not reside in the object, does it reside in the light that reaches our eye? Didn’t Newton prove that white light is composed of several colours? A version of this story enters the Lord of the Rings, when the wizard Saruman the White changes into Saruman of Many Colours. But if the colours are intrinsic to the wavelength of light, then how is it that we can combine two different colours to produce a third? And how is it that there are colour blind people? We know that the answer to both questions has to do with the colour receptors in our eyes, and their wiring in our brain. That’s the origin of many optical illusions involving colour. Insects and birds have more colour receptors than we have, so they see more “basic” colours, and an infinitely more variety of colours than we do. Octopuses have no receptors for colour, but are still able to see colour through a totally different mechanism. So colour does seem to be an arbitrary label which animals use as a convenient means of organizing their perception of colour. Colour does not seem to reside in the material of the external world, but only in the states of our minds.

Shakespeare is so often correct: “What’s in a name? That which we call a rose // By any other name would smell as sweet.” He provides an entry to our understanding of our senses as providing arbitrary and useful labels to understanding the world outside us. We live in Plato’s cave. We only see shadows of the world. The bees which harvest the nectar of flowers see a different shadow of the world. Even if they could talk to us, we might have a hard time understanding what they are saying. Which is the flower: the featured photo, or the one above? Or neither? Or does it really matter? Isn’t the beauty of the colours all that you want to enjoy?

Yellow=Red+Green

Like many others, I went through the usual art classes at school. But even before I took my first such class, someone may have told me that you mix yellow and blue pigments to make green. These joyful discoveries were made systematic in the art classes where we learnt how the primary colours of pigments are red, yellow, and blue. This was so ingrained in my thinking that I completely ignored the writings of Seurat even after I discovered his pointillist techniques later in school.

Spring leaves, Naukuchia Tal

I could have paid attention when my science teacher tried to tell us that the primary colours of light are different: red, blue, and green. When I did not, it was a steep learning curve for me as I grew interested in the stage during my years in college. I laboured at producing colours of light for plays using a completely wrong model for colours. I remembered the great surprise I had in producing a cold grey light for use in a play by mixing floods and spotlights. It was around then that I discarded the theory which worked for pigments.

Drying leaves in spring, Naini Tal

Now, of course, as we learn to use software for editing photos, the use of RGB colours has become so widespread that Seurat’s discoveries about colour seem commonplace. Still, when I discovered this spring that leaves use the same method I felt the pleasant tingling of discovery. The underlying colour of many leaves is red. The green colour is due to chloroplasts that the leaves produce to perform photosynthesis. When leaves die and the chloroplasts begin to decay, leaves turn yellow. If they don’t rot quickly you see them turning red as more and more chloroplasts die. In spring you see this in reverse. New leaves start out red, and grow chloroplasts, first turning yellow, and then green in a reversal of the changes that autumn brings. The first two photos in this post are of this transformation in new leaves. The photo above shows the changes in dying leaves.

Shikanji by the lake, Bhim Tal

An old friend, once an artist in his spare time, took a job which involved printers and the design of colours. As he worked with software and printers, trying to reproduce the colours produced in one domain in another, his interest in colour vision and reproduction grew. I listened to him talk about how subtractive schemes like CMY correspond to the print experience better, and what happens if you add on black ink. Now he spends much more of his time on his art, but spared some time to talk about what he found.

Fruits in a market stall, Bhowali

Colour vision is a property of human physiology and perception. So the fact that our eyes have receptors, the rods and cones, is part of the story. But behind this is a layer of computational nerves, a neural network, which combines the signals from these, and feeds it to yet other nerve cells which then transmit the information, through our optic nerves, to specialized areas in our brains. It is hard to believe how we see! Birds and insects see the world very differently. Photos of flowers or butterflies’ wings taken at wavelengths invisible to us show incredible patterns. This is an indication that in the ecology in which they exist, markers visible to non-humans are important. It is amazing how much detail the world shows once you zoom in to any part of it.