MX-PEX1 (serv.man12). Fiery PEX1 Colour Reference Guide - Sharp Copying Equipment User Guide / Operation Manual. Page 75

In the 1930s, the Commission Internationale de l’Eclairage (CIE) defined a standard 

, a way of defining colors in mathematical terms, to help in the communication of color 

information. This color space is based on research on the nature of color perception. The 
following CIE chromaticity diagram is a two-dimensional model of color vision. The arc 
around the top of the horseshoe encompasses the pure, or spectral, colors from blue-violet to 
red. Although the CIE chromaticity diagram is not perceptually uniform, some areas of the 
diagram seem to compress color differences relative to others, it is a good tool for illustrating 
some interesting aspects of color vision.

By mixing any two spectral colors in different proportions, we can create all the colors found 
on the straight line drawn between them in the diagram. It is possible to create the same gray 
by mixing blue-green and red light or by mixing yellow-green and blue-violet light. This is 
possible because of a phenomenon peculiar to color vision called 

. The eye does 

not distinguish individual wavelengths of light. Therefore, different combinations of spectral 
light can produce the same perceived color. 

Purple colors, which do not exist in the spectrum of pure light, are found at the bottom of the 
diagram. Purples are mixtures of red and blue light—the opposite ends of the spectrum. 

A color can be described in terms of three varying characteristics, called the 

 color model: 

• Hue: Tint (the qualitative aspect of a color—red, green, or orange)

• Saturation: The purity of the color

• Brightness: Relative position between white and black