Colours

If you can see colours that we call “blue, green, purple, pink, yellow, orange, and red,” then you are not colour blind. I know a colour-blind ornithologist who is brilliant at spotting well-camouflaged eggs and nestlings in ground-nesting birds. The reason is that his eyesight focuses on shapes and markings, rather than on colours. An example is the oval shape and scribble markings on an egg or chick of a Crowned Plover which nests on sand.

This is how our eyes see colour. At the back of the eye is a paper-thin membrane called the retina (from the Latin word rete meaning net). It is light-sensitive and contains tiny rod- and cone-shaped structures. Different colours have different frequencies. When their wavelengths touch the retina, the rods and cones trigger the optic nerve to send impulses to the brain. The brain interprets the rays’ frequency at lightning speed. Our memory recognises the received information as “colours” in general, as well as individual colours that we have learned to name in our growing up. Over time, our vocabulary expands to differentiate ‘turquoise’ from ‘blue,’ and ‘crimson’ from ‘pink.’

Before the English scientist John Dalton died in 1844, he requested a post-mortem analysis of his preserved eyeballs to explain his inherited sight difference. Scientists found his eyes to be “perfectly colourless.” According to the Royal Society 2024, when scientists re-examined Dalton’s eyeballs using DNA analysis in 1995, they discovered an absence of the gene that receives medium wavelength light.

Further testing using modern instruments has shown that more males than females are born colour blind. Fortunately, there are glasses now for correcting colour blindness. They are easily available and amazingly affordable!