While these basic principles are understood, the picture is complicated by the fact that there are several types of melanin, whose production varies according to the cell’s location in the body. Pheomelanin is a version that is pinker and features in red hair, the nipples, penis, and vagina. Eumelanin is more common and is found in skin, the iris, and most hair colors. Many genes are involved in the biochemical pathways that result in melanin production, and natural variation between people in the genes is the root cause of the spectrum of skin tones that humans have. Melanosomes vary in size
...more
