Poo, I submitted prematurely by slipping on the enter key...
Note that by "fair-haired" I include redheads and blonds.
Usually, the color of children's and adults' hair varies from pale yellow (blonde) to deep black. The ethnic distribution of colors has historically varied by geographic area. For example, deep brown and black prevail in the Middle East, North Africa, and Southern Europe, and even darker shades occur in East Asia, South Asia, as well as tropical (Sub-saharan) Africa and The Americas; lighter brown is more common in western, central and eastern Europe, yellow/blond in northern Europe, and reddish in the British Isles. However, considerable differences in hair color and texture exist between individuals of similar ethnicity, and immigration and global travel have greatly increased the diversity of hair characteristics in many countries.
At least two gene pairs control human hair color. One gene, which is a brown/blonde pair, has a dominant brown allele and a recessive blonde allele. If a person carries the brown allele, she will have brown hair; otherwise, she will be blonde. This also explains why two brown-haired parents can produce a blonde-haired child. The other gene pair is a not-red/red pair, where the "not-red" allele (which suppresses production of phaeomelanin) is dominant and the allele for red hair is recessive. Since the two gene pairs both govern hair color, a person with two copies of the red-haired allele will have red hair, but it will be either auburn or bright reddish orange depending upon whether the first gene pair gives a brown or blonde hair color respectively. The recessive genes for both brown/blonde and red hair are found nearly exclusively in populations of Whites and Caucasians.There is also a black gene, usually related to darker skinned humans. However, the two-gene model cannot explain the various shades of brown, blonde, or red which may occur (for example, platinum blonde versus dark blonde/light brown), or why one blonde child's hair might turn brown as he grows up while another blonde child's hair does not. According to some research, there are several gene pairs that control the light versus dark hair color in an accumulative effect. Therefore, the more of these that are dominant, the darker the hair will be.
https://en.wikipedia.org/wiki/Hair_color
