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 Grey on people. Doctors in this world are called "swatchmen", since they show of colour to their patients. Shades of green, especially Lincoln green, act as a narcotic, and are often abused as recreational drugs. Surnames and names of towns are usually derived from various shades of colour, such as jade, carmine and saffron. Protagonist Eddie Russett is a 'Red' sent to the outer-fringe town of East Carmine to conduct a chair census, which he speculates is punishment for a practical joke played on the son of a prefect. There he meets Jane, a Grey with an upturned nose and a