Which part of the hair is responsible for its color?

The correct answer focuses on the cortex and melanin, as these elements are primarily responsible for determining the color of hair. The cortex is the middle layer of the hair shaft and contains the majority of its mass. Within the cortex are pigment-producing cells called melanocytes, which produce melanin. Melanin is the natural pigment that gives hair its color, with different types and amounts of melanin resulting in varying shades, from blonde to black.

For instance, individuals with more eumelanin tend to have darker hair, while those with higher levels of pheomelanin will have lighter hair shades, such as blonde or red. The other layers, such as the cuticle, medulla, and hair bulb, do not play a direct role in determining hair color. The cuticle is the outer protective layer, the medulla is the innermost layer which may not even be present in all hair types, and the hair bulb, located at the base of the hair follicle, is more associated with hair growth than color. Thus, the interplay between the cortex and melanin is what truly defines hair color.