Can three lights make a new colour?

A different kind of mixing

Mixing coloured light does not work in the same way as mixing coloured paint. With light, you add light arriving at your eyes. This is called additive colour mixing.

Our game uses red, green and blue lights. In an idealised RGB model, combining these at suitable intensities produces the secondary colours and white.

Try two lights

Red and green light combine to appear yellow. Green and blue combine to appear cyan. Red and blue combine to appear magenta.

These are perceived colours produced by combinations of light. They are not a claim that the wavelengths themselves turn into a new single wavelength.

Add the third

In the game’s simplified model, red, green and blue together make white. Switch all three off and there is no emitted light.

The game represents these combinations with screen colours. Your display and its settings affect the appearance, so colour names are always shown too.

How screens use the idea

Many screens use tiny red, green and blue subpixels. Adjusting their brightness creates a wide range of perceived colours.

Our discovery lab keeps the model simple: each channel is either on or off. Real screens adjust channel intensities rather than limiting them to two states.

Explore without equipment

Try to make yellow, cyan, magenta and white in the light mixer. Predict which channels you need before selecting them.

Use the on-screen game only. Never point bright lights or lasers at anyone’s eyes, and never look directly at the Sun.

Further reading

• Exploratorium: Colored shadows