In which part of the hair do people with lighter colored hair have melanin?

Individuals with lighter colored hair typically have melanin concentrated in the cortex only. The cortex is the middle layer of the hair shaft and contains the majority of the hair's pigment, which gives hair its color. In lighter hair types, the amount of melanin is less dense compared to darker hair, leading to a lighter appearance.

The medulla, which is the innermost layer of the hair, may be absent in some hair types altogether, especially in finer or lighter hair. The cuticle, on the other hand, is the outermost layer and serves primarily as protection for the inner layers but does not contribute to hair color as it lacks pigment. Therefore, melanin presence and the role it plays in hair color is primarily related to the cortex, making this the correct answer. Understanding the structure of hair and the function of each layer is crucial for making sense of how hair color variations occur.