* Eumelanin: This determines how dark your hair is. More eumelanin means darker hair (black or brown). Different amounts and types of eumelanin result in different shades of brown.
* Pheomelanin: This determines how red or blonde your hair is. All hair has some pheomelanin, but higher concentrations result in red or blonde hair.
How it works:
Specialized cells called melanocytes produce melanin. These cells are located in hair follicles. The melanin is then incorporated into the cells that make up the hair shaft as it grows.
Genetics:
The amount and type of melanin your melanocytes produce are determined by your genes, which you inherit from your parents. Many different genes contribute to hair color, which is why there's such a wide range of natural hair colors.