A two-dimensional Cartesian plot that depicts the multidimensional subjective relationship among colors perceived by the normal human visual system (eyes and nervous system, including the brain) when additively stimulated by (two or more; usually three) discrete monochromatic visible sources (wavelengths. ) Note: The familiar CIE chromaticity diagram depicts perceived colors plotted as a function of the normalized relative intensity of a defined red (increasingly red with increased "X", or abscissa, value) versus the normalized relative intensity of a defined green (increasingly green with increased "Y". Or ordinate, value. ) With respect to a given perceived color, as plotted on the chromaticity diagram, the normalized relative intensity of a defined blue at any point is obtained by adding the normalized relative intensities of the red and green, and subtracting the total from 1.