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How does colour constancy allow an object to appear similarly coloured under different kinds of illumination?

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A circular RYB color wheel divided into twelve segments, showing a progression of colors from red, orange, and yellow to green, blue, and violet. — colour The RYB color model is being illustrated on a color wheel.

Colour constancy is a form of perceptual constancy that allows the human eye and brain to perceive an object as having a consistent colour despite changes in the spectral energy distribution of the light illuminating it.2

Because different light sources reflect varying energy distributions from an object, the brain performs a process of mental reconstitution to compensate for these differences. This "realistic" perception is largely determined by comparing the brightness and hue of an object against its surroundings. For example, an object is perceived to maintain its characteristic colour whether viewed in bright sunlight or under the low illumination of a cloudy sky.123

This ability is essential for identifying objects under diverse environmental conditions. However, this mechanism is not absolute; it can be influenced by factors such as limited experience with an object, a lack of environmental cues, or the phenomenon of metamerism, where objects that match in one type of light appear different under another.12