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 small amount of orange to a mixture of red and white will correct the tendency of this mixture to shift slightly towards the blue end of the spectrum). 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