A pure color is the color with the greatest saturation in each hue.
Colors can broadly be divided into achromatic colors such as white, grey and black, and chromatic colors, which are colors with hues, such as red, yellow and blue. Pure colors of the respective hues of chromatic colors, are colors of the solar spectrum (colors obtained by passing sunlight through a prism) with the greatest saturation. With pure colors, the saturation cannot be raised any higher.
Most colors are a mixture of colors of different wavelengths but the colors of the solar spectrum are “pure” colors which cannot be broken down any further. The level of purity and intensity of a color can be expressed in saturation. Achromatic colors (white, grey, black) are said to have zero saturation. This saturation value increases as the proportion of chromatic colors to achromatic colors increases. Colors produced by mixing black or white to a pure color are called clear colors. These correspond to colors on the surface of a color solid. Colors produced by mixing grey to a pure color are called turbid colors. These correspond to colors on the inside of a color solid.
Generally, paints which have not been mixed with other colors may also be referred to as pure colors.