CIE Colour Gamut The colour gamut diagram is a way of visualizing the three dimensional colour space. If the primary colours of a system are A, B and C then we can express each real colour as a mixture of those primaries. Mathematically the colour 'coordinates' in the gamut for any mixed colour is given by x=A/(A+B+C) y=B/(A+B+C) z=C/(A+B+C) and x+y+z=1 Since we usually know the primaries of the system (e.g. designing the colour filter for a liquid crystal display) we thus know the x and y coordinate which is shown on the CIE colour gamut (z can be calculated by using the last conditions).