When you see men who have a full grown beard, some of them, even after they shave, have this visible difference in color from the rest of their face. Is it because they don't shave good enough or is it because of another reason?
Hair color is not always even. Some people have different hair, beard, or even pubic hair color. It can be due to genetics, dying one's hair or the changing of hair color due to age. Sometimes when hairs develop will influence what color they will take on. Thus, the hairs that develop when you are born may be a different color than the hairs you develop during your teenage years. And hairs change color as you get older (the most obvious one is turning grey).