<P> The color of light (i.e., the spectral power distribution) reflected from illuminated surfaces coated in paint mixes, slurries of pigment particles, is not well approximated by a subtractive or additive mixing model . Color predictions that incorporate light scattering effects of pigment particles and paint layer thickness require approaches based on the Kubleka--Munk equations . Even such approaches cannot predict the color of paint mixtures precisely since small variances in particle size distribution, impurity concentrations etc. can be difficult to measure but impart perceptible effects on the way light is reflected from the paint . Artists typically rely on mixing experience and "recipes" to mix desired colors from a small initial set of primaries and do not use mathematical modelling . </P> <P> There are hundreds of commercially available pigments for visual artists to use and mix (in various media such as oil, watercolor, acrylic, and pastel). A common approach is to use just a limited palette of primary pigments (often between four and eight) that can be physically mixed to any color that the artist desires in the final work . There is no specific set of pigments that are primary colors, the choice of pigments depends entirely on the artist's subjective preference of subject and style of art as well as material considerations like lightfastness and mixing heuristics . Contemporary classical realists have often advocated that a limited palette of white, red, yellow, and black pigment (often described as the "Zorn palette") is sufficient for compelling work . </P> <P> A chromaticity diagram can illustrate the gamut of different choices of primaries, for example showing which colors are lost (and gained) if you use RGB for subtractive color mixing (instead of CMY). </P> <P> A contemporary description of the color vision system provides an understanding of primary colors that is consistent with modern color science . The human eye normally contains only three types of color photoreceptors, known as long - wavelength (L), medium - wavelength (M), and short - wavelength (S) cone cells . These photoreceptor types respond to different degrees across visible electromagnetic spectrum . The S cone response is generally assumed to be negligible at long wavelengths greater than about 560 nm while the L and M cones respond across the entire visible spectrum . The LMS primaries are imaginary since there is no visible wavelength that stimulates only one type of cone (i.e., humans cannot normally see a color that corresponds to pure L, M or S stimulation). The LMS primaries are complete since every visible color can be mapped to a triplet specifying the coordinates in LMS color space . </P>

What are the primary colours in visual arts