The human eye and brain work together to translate light into the colours we perceive around us every day. The eye’s light receptors transmit messages to the brain to produce our everyday world.

Reflections, light and colours

Colours are not inherent in objects. Rather, the surface of an object will reflect some colours and absorb others, leaving us to perceive only the reflected colour.

  • For example, the colour red isn’t ‘in’ an apple. The apple’s surface is reflecting the wavelengths our eyes perceive as red and absorbing others. If an object appears white, that is because it reflects all wavelengths. Conversely, if an object appears black, then it absorbs all colours.

Red, green and blue: primary colours of the colour spectrum

By combining these coloured lights in equal amounts, you can produce pure white light. If you were to vary the amounts of red, blue and green light, you can produce all the colours in the light spectrum.

Eyes, rods and cones

Your retinas are covered by millions of light sensitive cells- some shaped like rods and some shaped like cones. These cells process light into nerve impulses before passing them along the optic nerve to the cortex of the brain.

Interestingly, the human eye is able to perceive more variation of warmer colours as opposed to cooler colours. This is due to almost two-thirds of the cones in your eyes process longer wavelengths of light (yellows, oranges and reds).

Colour blindness

1% of women and 8% of men are estimated to have some form of colour blindness. The majority of people who have some form of colour deficiency are unaware that the colours they see as identical are in fact different. Most people who have some form of colour blindness will still perceive different colours; they’re just transmitted to the brain in a different way.

The most common form of colour blindness is red and green dichromatism, which leaves a person unable to distinguish between red and green. Other colour-pairs of colour blindness can occur, but aren’t as common.

Total colour blindness is very rare.

Colour and nature

Other mammals, along with birds and fish can all perceive the entire colour spectrum. Bees and some other insects can even see ultraviolet colours, invisible to the human eye.

Colour camouflage is one of nature’s most prominent survival tactics, relying on the ability of a predator to be unable to distinguish colour.

One of the most common assumptions about colour and nature is that dogs see in black and white. Recent studies suggest, however, that dogs can differentiate between blue and red, even being able to notice subtle differences between shades of violet and blue.