Pheomelanin in the context of "Red hair"

Red hair, also known as ginger hair, is a human hair color found in 2–6% of people of Northern or Northwestern European ancestry and smaller amounts in other populations. It is most common in individuals homozygous for a recessive allele on chromosome 16 that produces an altered version of the MC1R protein.

Red hair varies in hue from a deep burgundy or bright copper, or auburn, to burnt orange or red-orange to strawberry blond. Characterized by high levels of the reddish pigment pheomelanin and relatively low levels of the dark pigment eumelanin, it is typically associated with fair skin color, lighter eye color, freckles, and sensitivity to ultraviolet light.

Brown hair, also referred to as brunette (when female), is the second-most common human hair color, after black hair. It varies from light to dark brown. It is characterized by higher levels of the dark pigment eumelanin and lower levels of the pale pigment pheomelanin.

Brown hair is common among populations in the Western world, especially among those from Northwestern Europe and the United States, as well as populations in Central Europe, Southeastern Europe, Eastern Europe, Southern Europe, Southern Cone, Brazil, Colombia, Costa Rica, Puerto Rico, and also some populations in the Middle East, Central Asia, Afghanistan and South Asia where it transitions smoothly into black hair. Additionally, brown hair is common among Australian Aboriginals and Melanesians.

Auburn hair is a human hair color, a variety of red hair, most commonly described as reddish-brown in color. Auburn hair ranges in shades from medium to dark. It can be found with a wide array of skin tones and eye colors. The chemical pigments that cause the coloration of auburn hair are often pheomelanin with high levels of eumelanin.