Which part of the hair contains the pigment that determines color?

The cortex is the part of the hair that contains the pigment responsible for determining hair color. This layer is situated between the cuticle (the outermost layer) and the medulla (the innermost core of the hair).

The pigment contained within the cortex is called melanin, which comes in different forms and concentrations, influencing the hair's color. Darker hair possesses more eumelanin, while lighter hair, particularly shades of blonde or red, results from varying amounts of pheomelanin. The distribution and mix of these pigments give rise to the wide variety of hair colors seen in individuals.

The cuticle serves primarily as a protective layer, helping to shield the more fragile cortex and medulla underneath. The medulla, while present in some hair types, generally does not play a role in pigmentation; it can be absent in finer hair types altogether. Meanwhile, the follicle is the part of the skin where the hair grows and does not contribute directly to the color of the hair itself.