Eumelanin in the context of "Tyrosine"

A biological pigment, also known simply as a pigment or biochrome, is a substance produced by living organisms that have a color resulting from selective color absorption. Biological pigments include plant pigments and flower pigments. Many biological structures, such as skin, eyes, feathers, fur and hair contain pigments such as melanin in specialized cells called chromatophores. In some species, pigments accrue over very long periods during an individual's lifespan.

Pigment color differs from structural color in that it is the same for all viewing angles, whereas structural color is the result of selective reflection or iridescence, usually because of multilayer structures. For example, butterfly wings typically contain structural color, although many butterflies have cells that contain pigment as well.

Light skin is a human skin color that has a low level of eumelanin pigmentation as an adaptation to environments of low UV radiation.Due to migrations of people in recent centuries, light-skinned populations today are found all over the world. Light skin is most commonly found amongst the native populations of Europe, East Asia, West Asia, Central Asia, South Asia, Siberia, and North Africa as measured through skin reflectance. People with light skin pigmentation are often referred to as "white", but the majority of countries officially categorize people by ethnic or national origin and not by perceived skin tone. Furthermore, definitions and perceptions of "ethnicity" or "race" vary greatly from country to country.

Humans with light skin pigmentation have skin with low amounts of eumelanin, and possess fewer melanosomes than humans with dark skin pigmentation. Light skin provides better absorption qualities of ultraviolet radiation, which helps the body to synthesize higher amounts of vitamin D for bodily processes such as calcium development. On the other hand, light-skinned people who live near the equator, where there is abundant sunlight, are at an increased risk of folate depletion. As a consequence of folate depletion, they are at a higher risk of DNA damage, birth defects, and numerous types of cancers, especially skin cancer. Humans with darker skin who live further from the tropics may have lower vitamin D levels, which can also lead to health complications, both physical and mental, including miscarriage and a greater risk of developing schizophrenia. These two observations form the "vitamin D–folate hypothesis", which attempts to explain why populations that migrated away from the tropics into areas of low UV radiation evolved to have light skin pigmentation.

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.

Blond (MASC) or blonde (FEM), also referred to as fair hair, is a human hair color characterized by low levels of eumelanin, the dark pigment. The resultant visible hue depends on various factors, but always has some yellowish color. The color can be from the very pale blond (caused by a patchy, scarce distribution of pigment) to reddish "strawberry" blond or golden-brownish ("sandy") blond colors (the latter with more eumelanin). Occasionally, the state of being blond, and specifically the occurrence of blond traits in a predominantly dark or colored population are referred to as blondism.

Because hair color tends to darken with age, natural blond hair is significantly less common in adulthood. Naturally occurring blond hair is primarily found in people living in or descended from people who lived in Northern Europe, and may have evolved alongside the development of light skin that enables more efficient synthesis of vitamin D, due to northern Europe's lower levels of sunlight. Blond hair has also developed in other populations, although it is usually not as common, and can be found among the native populations of the Solomon Islands, Vanuatu, and Fiji; among the Berbers of North Africa; and among some Asian people.

Black hair is the darkest and most common of all human hair colors globally, due to large populations with this trait. This hair type contains a much more dense quantity of eumelanin pigmentation in comparison to other hair colors, such as brown, blonde and red. In English, various types of black hair are sometimes described as soft-black, raven black, or jet-black. The range of skin colors associated with black hair is vast, ranging from the palest of light skin tones to dark skin. Black-haired humans can have dark or light eyes, but more commonly dark.