First of all, the coat color of hamster is determined by the pigment in its body. When hamsters grow up, the pigment cells in their bodies secrete melanin, which makes their hair appear black. This is a natural physiological process.
Secondly, the coat color of hamster is also influenced by genetic factors. The coat color of hamsters is hereditary, and the genes of parents hamsters will be passed on to their offspring, thus affecting their coat color. If the parents hamster has the gene of black hair, then the offspring's hair is likely to appear black.
In addition, environmental factors may also have some influence on the coat color of hamsters. For example, improper diet or poor living environment may cause hamster hair to become dull. Therefore, in order to keep the hamster's coat color healthy and bright, it is necessary to provide a good diet and living environment.