Question

Why can't we differentiate between colours at night?

Answer 1

We cannot differentiate between colours at night because colour perception is mediated exclusively by cone cells, which are sensitive only to bright light (photopic vision) and contain pigments for detecting red, green, and blue wavelengths. In the dark or under dim lighting, cones remain unexcited and only rod cells become active, which are responsible for twilight (scotopic vision) but are completely incapable of distinguishing different hues.