Cathode ray tube colour gamut. This graphic represents the range of colours produced by a cathode ray tube (CRT). The gamut (triangular) is typically less than the entire available colour space, here represented by the larger outline shape. The corners of the gamut for a CRT depend on the colours produced by the phosphors on the CRT screen. In this case, this is an RGB (red, green and blue) display. The central area produces a white colour. Graphic produced at the National Physical Laboratory, UK.