First of all, people's hair is yellow or white, and there is no melanin, especially in the sun, people's hair will appear yellowish brown, and hair that can turn black in the sun is rare. Because of natural selection, pure black hair is not suitable for survival.
In your case, eat more black sesame seeds or black sesame paste, because the skin of black sesame seeds contains a lot of melanin, and the oil content of sesame seeds is relatively high, which is easy to absorb melanin.