Chroma (from Greek 'chroma': colour, complexion) refers to the saturation or intensity of a colour — how pure it is, how free from grey or white or black. It is one of three dimensions of colour in the Munsell colour system, along with hue (the particular colour — red, blue, yellow) and value (the lightness or darkness). High-chroma colours are vivid and saturated; low-chroma colours are muted, greyed, close to neutral. The distinction matters enormously in painting: Monet's late Water Lilies use colours of moderate chroma that allow complex optical mixing; Matisse's Fauvist paintings use maximum-chroma primaries and secondaries applied flat, without tonal modulation. In digital design and photography, chroma is equivalent to saturation in the HSB model. Understanding chroma separately from hue and value is fundamental to colour mixing and colour theory.