What gives the tan or brown color to the skin?

The tan or brown color of the skin is primarily due to melanin, which is a pigment produced by melanocytes located in the epidermis, the outer layer of the skin. Melanin is responsible for the color of the skin, hair, and eyes, and it plays a crucial role in protecting the skin from harmful ultraviolet (UV) radiation from the sun. When the skin is exposed to UV rays, melanocytes produce more melanin to absorb and dissipate the damaging rays, resulting in a tanned appearance.

Collagen, although important for skin structure and elasticity, does not contribute to the coloration of the skin. Sebum is an oily substance that helps keep the skin moisturized but is not involved in the pigmentation process. Keratin is a type of protein that is a key component of hair, skin, and nails, providing structural support, but it also does not impart color to the skin. Thus, melanin is the correct answer, as it is the pigment responsible for the varying shades of brown and tan in human skin.