Seeing Colours Combine

See two ways of mixing colours, and how each affects the spectrum of light.

How to Use It

Slide filters into the slots to remove colour from a white light box. Use buttons to add colour to a dark box.

What Science Tells Us

Human eyes typically have three types of colour receptor: ones most sensitive to long wavelengths (red light); ones most sensitive to medium wavelengths (green light); and ones most sensitive to short wavelengths (blue light). Both additive and subtractive colour mixing control how much light falls on each of these receptor types, but from opposing starting points.

Additive colour mixing simply adds a little of each colour—red, green or blue—to stimulate each receptor type in just the right way to create a certain mix.

Subtractive colour removes a little of each colour—red, green or blue—from white light so that what is left over stimulates each receptor type in just the right way. Removing red light results in a cyan appearance, so pigments that absorb red light appear cyan in colour. Removing green light results in magenta, and removing blue light results in yellow.

Things to Try or Ask

 What happens if you place the filters over the ‘additive’ lights and turn them on?

 What happens if you place the filters over a phone or tablet screen?

Finding the Science in Your World

Your printer mixes colour the same way as the filters: with yellow, cyan, and magenta inks. Your TV and mobile phone screens mix colour the same way as the lights, with red, green, and blue pixels.