In the study of the perception of color, one of the first mathematically defined color spaces was the CIE 1931 XYZ color space, created by the International Commission on Illumination (CIE) in 1931.
The diagram below represents all of the chromaticities or colors that are visible to the average person. The gamut (range of colors) of all visible chromaticities on the CIE plot is the tongue-shaped or horseshoe-shaped figure. The curved edge of the gamut is called the spectral locus and corresponds to monochromatic (absence of color) light, with wavelengths listed in nanometers. The straight edge …