What is colour?

Is colour just light? Or is it what we see when our brain and eyes respond to light? Without our eyes to see and our brains to interpret, would there be colour?

We see colour all around us. It is so much a part of our experience that rainbows and other colour phenomena are interwoven into the beliefs of many peoples and cultures.

Recipe for a rainbow

White light contains all the colours of the rainbow. You can see these colours by shining a white light through a glass prism. When a beam of white light shines through a prism, it is split into the colours of the rainbow.

These colours are called the colour spectrum. Each colour in the spectrum bends at a different angle as it passses through the prism. As a result, the colours are separated from each other.

diagram of light through a prism

The rainbow serpent

Can you imagine a brilliantly coloured serpent with the body of a snake, the tail of a crocodile, the chest of an emu, the ears of a kangaroo and skin like shimmering snake scales? This is a Rainbow Serpent, the Being many Aboriginal people believe created the universe.

The Rainbow Serpent symbolises the creative and destructive forces in nature. It has a varying form, made from animal and sometimes human parts. There are many versions of the Serpent, each representing central elements of nature: the sky is evoked by rainbows and flying foxes, the land by snakes and the sea by pipefishes.

A 4000-6000-year-old depiction of the Rainbow Serpent. Many of its characteristics are similar to the Ribboned Pipefish. Kakadu National Park

Why is the sky blue?

When sunlight passes through the atmosphere, some of it bounces off particles in the air and scatters in all directions. Blue light scatters more easily than the other colours. As the blue light scatters, it illuminates the atmosphere, making it appear blue. The other colours are scattered less and tend to pass right through the atmosphere. The sun appears pale yellow because the light reaching us is mostly white light with some of the blue removed by scattering.

diagram of light passing through earths atmosphere showing blue light scattering

Why are some sunsets red?

At dusk, when the sun is low on the horizon, sunlight passes through more atmosphere to reach us than during the day. By the time the light reaches us, more of the colours have been scattered. The last colour to be scattered is red. If there are many particles in the air (due to pollution, dust or smoke), the sun and sky can appear red in the middle of the day.

diagram of light passing through earths atmosphere with red light scattering last