Colour constancy is the ability to perceive colours as relatively constant, even under changing lighting conditions.
Colour constancy refers to the perceptual ability to compensate when changes in illumination would otherwise cause things to appear to be change colour.
Colour constancy is an extreme case of chromatic adaptation that associates a particular colour with an object regardless of changes in lighting.
Colour vision relies on colour constancy as it allows us to perceive the colour of an object as stable, even when the intensity or spectral distribution of the illumination changes.