Representation of color for human vision

Trichromacy of Vision Color Mixture

            Let denote the spectral power distribution (in watts /m² /unit wavelength) of the light emanating from a pixel of the image plane, and  the wavelength. The human retina contains pre-dominantly three different color receptors (called cones) that are sensitive to 3 overlapping areas of the visible spectrum.  The sensitivities of the receptors peak at approximately 445. (Called blue), 535 (called green) and 570 (called red) nanometers. 

Each type of receptors integrates the energy in the incident light at various wavelengths in proportion to their sensitivity to light at that wavelength. The three resulting numbers are primarily responsible for color sensation. This is the basis for trichromatic theory of color vision, which states that the color of light entering the eye may be specified by only 3 numbers, rather than a complete function of wavelengths over the visible range. This leads to significant economy in color specification and reproduction for human viewing. Much of the credit for this significant work goes to the physicist Thomas Young. 

The counterpart to trichromacy of vision is the Trichromacy of Color Mixture.

            This important principle states that light of any color can be synthesized by an appropriate mixture of 3 properly chosen primary colors.

Maxwell in 1855 showed this using a 3-color projecting system. Several development took place since that time creating a large body of knowledge referred to as colorimetry.

Although trichromacy of color is based on subjective & physiological finding, these are precise measurements that can be made to examine color matches.