Dose of STEM: The World in Colour

“There’s a reason we don’t see the world in black and white” ~ Celerie Kemble

From the comforting tranquillity of the blue sky to the breathtaking flamboyance of the rainbow, we see colour everywhere. But what is this colour that we perceive? And like beauty, is this also something that is only in the eye of the beholder?

Science of colour perception

The human eye has three different types of photoreceptors (cones) in the retina. These have photosensitive pigments that react to light. Each cone is sensitive to either red, blue or green light. When different wavelengths of light enter the eye, these cells send signals to the brain. The brain then superimposes the signals to produce the sensation of colour.

So essentially, colour is just the brain’s way of perceiving the different kinds of light. A very small range of the electromagnetic spectrum, known as the visible spectrum (wavelength 380-750 nm), is what a typical human eye responds to. Wavelengths just lower than this are called Ultraviolet and those just higher are called Infrared.

Evolution of colour vision in humans

Ancient mammals lived with very limited colour vision. As far back as 90 million years ago, human ancestors are believed to have seen the world using Ultraviolet vision. About 30 million years ago, human ancestral genes evolved to possess trichromatic colour vision. Several environmental changes combined with genetic mutations in visual pigments over millions of years resulted in human vision improving from a shadowy perspective to the vivid view we now have.

Some of the evolutionary advantages of colour vision are:

Enhanced techniques for foraging - Ripe fruits could be easily spotted from great distances
Better ability to spot threats - better equipped to identify camouflaged predators
Ability to find what is necessary in regions of cluttered natural vegetation

Colour Blindness

This refers to an absence or reduction in the ability to normally perceive colours. It happens when one or more of the three types of cones in the retina don’t function appropriately. The most common cause is heredity and inherited colour blindness has no cure. On the other hand, if it is acquired due to other external causes (such as eye or brain diseases and injuries), then treating this can help reduce the symptoms.

Contrary to popular belief, colour blindness can actually be of great advantage in several situations. Vincent Van Gogh, for example, was able to create extremely graphic and colourful artwork, despite being believed to have been colour blind.

Some advantages of Colour blindness are:

Helps detect Camouflage - The eye becomes more sensitive to subtle changes in shades
Good pattern recognition ability
Greater attention to details in an image - While those with normal vision might focus on certain bright or appealing parts of an image, colour-blind people focus on more of the details
Colour-blind people are less distracted by colour - For example, bright and colourful advertisements appeal less to them than they do to people with normal vision.

Over the span of our lives, we view a myriad of different colours that add depth, dimension and a stomach flipping sensation of entrancing splendour to the world around us. With the capacity to influence us psychologically as well as emotionally, colours make up an integral part of our existence and sometimes, all it takes is a momentary pause to observe nature’s gifts to us.

“Colours are the smiles of nature” ~ James Henry Leigh Hunt

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