A spectrum of colours
Physics Narrative for 11-14
Noticing and accounting for colour
A white light source emits a whole range of frequencies. You can select some frequencies by filtering or by dispersion. These selected beams will all be of a limited range of frequencies, and so close to one spectral colour.
Paint has a particular colour because it only reflects a certain range of frequencies. If that range is not in the beam shone on the paint, then nothing gets reflected.
The eye has only three colour sensors: hence the three-colour theory of vision. Different combinations of spectral colours can all appear to be the same perceptual colour.