Melanin in Hair: Understanding Eumelanin & Pheomelanin

There are two main types of melanin found in human hair:

* Eumelanin: This is responsible for brown and black hair colors. The more eumelanin present, the darker the hair.

* Pheomelanin: This is responsible for red and yellow hair colors. All hair contains pheomelanin, but it is more prominent in redheads.

Therefore, the answer is two.