Human hair color account for all possible shades of brown, blond, or red (for example, platinum blond versus dark blond/light brown), nor does it explain why hair color sometimes darkens as a person ages. Several gene pairs control the light versus dark hair color in a cumulative effect. A person's genotype for a multifactorial trait can interact with the environment to produce varying phenotypes (see quantitative trait locus). Natural hair color can be brown, blond, black, red, or white; all natural hair colors including grey, white and lightest blond, are shades of brown. The Fischer–Saller scale, named after Eugen Fischer and , is
Tints and shades Tints and shades In color theory, a tint is a mixture of a color with white, which reduces darkness, while a shade is a mixture with black, which increases darkness. Both processes affect the resulting color mixture's relative lightness. A tone is produced either by mixing a color with grey, or by both tinting and shading. Mixing a color with any neutral color (including black, gray and white) reduces the chroma, or colorfulness, while the hue remains unchanged. In common language, the term "shade" can be generalized to furthermore encompass any varieties of a particular color, whether technically they are