Hi, Thanks for writing in to us. Skin of an individual depends on the amount of melanin, a pigment present in skin which gives color. The shade of skin is determined genetically by the amount of melanin present. In certain areas like penis and lips, there is mucosa and non keratinized skin which is why they are still pink in color. After circumcision keratinization may occur in part of the operated scar where subsequently color change takes place. This is a normal happening. Hope your query is answered