Have you ever wonder Why are blacks not blond? Simple reason: because their bodies are making too much melanin.
In humans, like in other mammals, hair color is determined by two groups of pigments: eumelanin (black and gray tones) and pheomelanin (all shades of red). The same substances are responsible for skin pigmentation: sunburn, freckles, etc.
In some human races living in hot climates (Africans, Papuans, Australian aborigines), eumelanin synthesize especially intensively, so their skin is dark. It believes in protecting against solar ultraviolet radiation.
Simultaneously, many pigments inevitably get into the hair so that all dark-skinned people turn out to be brunettes. With age, the synthesis of melanins can stop in people of any race, and the hair will turn gray.
The complete absence of pigment in hair and skin (albinism) occurs with some genetic mutations. But no one can call a gray-haired man or an albino blond since blond hair does contain a certain amount of pigments.
In earlier times in Africa, albinos were often expelled from communities, considering their appearance suspicious, forcing them to marry only with each other. In other parts of Africa, there are still albino Negro villages.