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
Shades of gray metallic" was formulated in 1999. The color displayed at right matches the color sample called "taupe" referenced below in the 1930 book "A Dictionary of Color", the world standard for color terms before the invention of computers. However, the word "taupe" may often be used to refer to lighter shades of taupe today, and therefore another name for this color is "dark taupe". The first use of "taupe" as a color name in English was in the early 19th century. Shades of gray Variations of gray or grey include achromatic grayscale shades, which lie exactly between white and black, and