Chroma
How strong and pure a colour looks compared with a grey of the same lightness.
Also: colourfulness, intensity
Chroma measures the strength of a colour. A fire engine has high chroma; a brick has a similar hue but much lower chroma; a grey stone has none. The word comes from the Greek for colour. Painters lower chroma by mixing in grey or the opposite colour on the wheel. Chroma is closely related to saturation, and in everyday speech the two are used as if they were the same. In colour science chroma is judged against a white reference, while saturation is judged against the colour's own brightness.