Final answer:
Melanin is mainly found in the cortex of the hair, which is the second or middle layer of the hair shaft, responsible for the hair's color and texture.
Step-by-step explanation:
Melanin, the pigment that determines the color of hair and skin, is mainly located in the part of the hair known as the cortex. The hair shaft has three layers: the cuticle in hair is the outermost layer, the cortex in hair is the second or middle layer, and the innermost layer is called the medulla. While the medulla forms the central core of the hair, surrounded by the cortex, and the cortex itself is covered by the cuticle, it is the cortex that contains the majority of melanin, contributing to the hair's color and texture.