Colour constancy, also known as chromatic adaptation, refers to the human brain's ability to perceive an object's colour consistently regardless of changes in lighting conditions. Synonyms for colour constancy include chromatic constancy, colour stability, colour fidelity, and colour perception. These concepts all refer to the phenomenon whereby people perceive coloured objects as having a constant hue, regardless of variations in the illumination. This ability is crucial to our ability to recognise and classify objects in the world around us. It allows us to perceive the true colour of objects under different lighting conditions, making our visual experience more consistent and reliable. Understanding colour constancy is essential in fields such as photography, computer vision and designing for visual perception.