Chromaticity (or Chroma) is the quality of a colour which determines whether it is perceived as vivid or startling. It is a measure of a colour's purity and similar in some ways to saturation. A colour that contains no white, grey or black is regarded as having a high chromaticity, and one which has significant white, grey or black content is described as having low chromaticity. In the diagram, the four top rectangles contain colours featuring high chromaticity. They are vivid and the colours are very pure. The lower four rectangles contain a large elements of white, grey or black and are therefore described as having low chromaticity.