The human skin color depends mainly on a single pigment called the melanin. To some extent the skin color depends on blood circulating in the part of body too. A blush of pink and pallor of death as well as angry red are all too familiar to us. Melanin is in cells of skin called melanocytes. They are located in epidermis, especially in the Stratum basale and in the hair follicles.
Melanocytes produce the melanin.
It uses the raw material - an amino acid called, tyrosine, to make the melanin. From the melanocytes the melanin emigrates to keratinocytes. This journey takes about 50 days for these cells. The melanin surrounds the nucleus of a keratinocyte and thus gives protection to them from ultra-violet radiation. Exposure to sunlight has a tanning effect i.e. the sun exposed skin darkens.