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
Michael M. J. Fischer Michael M. J. Fischer Michael M. J. Fischer is Andrew W. Mellon Professor in the Humanities and Professor of Anthropology and Science and Technology Studies at the Massachusetts Institute of Technology, and Lecturer in the Department of Global Health and Social Medicine, Harvard Medical School. He has done anthropological fieldwork in the Caribbean (Jamaica), the Middle East (Iran), South Asia (India), Southeast Asia (Singapore) and the United States on social change and religion (Protestants and Afro-Caribbean religions in Jamaica; Zoroastrians, Shi'ites, Baha'is, Jews in Iran; Jains and Parsis in India); on bazaars, merchants, craftsmen, and agriculture in Iran, Jamaica, India,