The Science of Color

A World Full of Colour

Look around you. You might see a green plant, a blue sky, a red jumper or a yellow pencil. Our world is bursting with colour. But have you ever wondered what colour really is? Where does it come from, and why does grass look green while the sea looks blue?

The answer is hidden in something you might not expect: light. In this book we will discover that colour is really made of light, that white light hides a whole rainbow inside it, and that your own eyes and brain do some amazing work to let you enjoy all the colours of the world.

Chapter 1: No Light, No Colour

Here is a simple but surprising fact: in complete darkness, there are no colours at all. Imagine going into a room with no windows and turning off every light. You could not tell a red ball from a blue one. Everything would just be black.

That is because colour comes from light. Light is a kind of energy that travels from glowing things like the Sun, a lamp or a fire. When light shines on the world and bounces into your eyes, you can see — and you can see colour. Turn the light off, and the colours vanish. So the very first secret of colour is this: no light, no colour.

Chapter 2: The Rainbow Inside White Light

The light from the Sun looks white or colourless. But here is something amazing: white light is really a mixture of all the rainbow colours stirred together. Hidden inside that plain white light are red, orange, yellow, green, blue and violet.

You can prove it. After rain, when the Sun comes out, tiny droplets of water in the air split the sunlight apart and spread it into a giant rainbow. A special glass shape called a prism does the same thing indoors. The light goes in white and comes out as a beautiful band of colours. The famous scientist Isaac Newton used a prism to show this hundreds of years ago, and proved that the rainbow was always hiding inside ordinary sunlight.

Chapter 3: Why Things Look Coloured

If colour comes from light, why does a banana look yellow and the grass look green? The secret is that objects do something clever with light. When light lands on something, the object bounces some colours back and soaks up the rest.

A banana soaks up most of the colours in the light but bounces yellow light back to your eyes — so it looks yellow. Grass bounces back green and absorbs the rest. A red apple reflects red and drinks in the others. And something that looks black is soaking up nearly all the light, while something white is bouncing nearly all of it back. So an object's colour is really about which colours of light it sends back to you.

Chapter 4: How Your Eyes See Colour

To see all this colour, you have two wonderful tools: your eyes. At the back of each eye is a patch covered in tiny light-catchers. Some of them are special colour-catchers called cones.

You have three kinds of cones. One kind notices red light, one notices green, and one notices blue. When light enters your eye, these cones send tiny signals to your brain. Your brain mixes the signals together and decides what colour you are seeing. By blending just red, green and blue in different amounts, your brain can build every colour you have ever seen — from sunset orange to deep purple. This is the same trick a television or phone screen uses, mixing tiny red, green and blue dots to make all its pictures.

Chapter 5: Mixing Colours

Artists love to mix colours too, but with paint it works a little differently. With paint, three colours called primary colours can be mixed to make many others. Red and yellow make orange. Yellow and blue make green. Blue and red make purple. Mixing colours like this is one of the first things artists learn, as you can read in The Story of Art.

Why is paint different from light? Remember, paint gets its colour by soaking up light. The more paints you mix together, the more light they soak up — which is why mixing lots of paints often gives a muddy brown. Light is the opposite: mix all the colours of light together and you get bright white again.

Chapter 6: Colour All Around Us

Colour is not just beautiful — it is useful, and it is everywhere in nature. A bright red ladybird warns birds, "Don't eat me, I taste bad!" Flowers wear bright colours to invite bees to visit. A green frog hides among green leaves so a hungry bird cannot spot it. Animals use colour to hide, to warn and to find each other.

People use colour with meaning too. Red can mean stop or danger. Green often means go or safe. We paint our rooms, choose our clothes and decorate our world with colours that make us feel happy. Colour is one of the first things artists, designers and even nature itself reach for.

So the next time you see a rainbow, a red apple or a blue sky, you will know the secret. Colour is a gift of light, bounced and split and caught by your amazing eyes — a rainbow hiding in plain sunlight, waiting for you to see it. You can discover more about light itself in The Story of Light.

Words to Remember

• Light: the energy that lets us see and makes colour possible.
• Prism: a glass shape that splits white light into rainbow colours.
• Reflect: to bounce light back, which gives an object its colour.
• Cones: the colour-catchers in your eye that notice red, green and blue.
• Primary colours: the few paint colours you can mix to make many others.