Well actually the darker a person's hair color is, the more individual hair follicles they have on their scalp as well!
I just brown hair.  I wonder how many people have brown hair. Next to black hair, it's actually the second-most common hair color. Is there a reasons so many people have brown hair? I don't know why large numbers of them do, but I know that in general eumelanin controls how dark hair is. The more there is, the darker the hair. Does the color of the hair change anything else about it?
The darker a person's natural hair color is, the more individual hair follicles they have on their scalp.