Colour vision

Color vision is the capacity of an organism to distinguish objects based on the wavelengths (or frequencies) of the light they reflect, emit, or transmit.

Color is a quality made by the visual brain and so it is not a property of objects, despite what children are taught.^[1]

The wavelength reflected from an object is the objective fact: it does not depend upon perception. A 'red' apple does not emit red light.^[2] Rather, it simply absorbs all the frequencies of visible light shining on it except for a group of frequencies that are reflected. It is these frequencies which are seen or perceived as red.

1. ↑ If this is doubted, remember that there are animals which cannot see colors, or who only see one or two colors.
2. ↑ Wright, W.D. (1967). The rays are not coloured [sic]: essays on the science and vision and colour [sic]. Bristol: Hilger. ISBN 0-85274-068-9.