Face it you are still babe as you get older the facial hair will thicken. For many males is seems in direct proportions to hair loss on the top of their heads. But some people do have naturally different hair colors. I guess they are brindle humans. My cousin has dark curly brown head hair, mustache and a bright red beard hair. It is really funny but he prefers to sport the two tone look. It all depends on heredity I suppose.
We had this guy in school who had a circular pattern of white hair on his head. It was visible as such because he wore his hair very short. His nickname was spot.