Melanocytes are specialized cells that produce melanin, the pigment responsible for skin color, while keratinocytes are the predominant cell type in the outer layer of the skin. When keratinocytes accumulate melanin granules on their superficial portion, they create a protective layer that absorbs and reflects harmful UV radiation, thereby reducing the risk of skin damage and skin cancer. This collaboration is crucial for the skin's defense against UV exposure, as it helps to shield deeper layers of skin from potential harm.