0_Apprentice
I just brown hair.  I wonder how many people have brown hair.
1_Wizard
Quite a lot!  It's actually the second most common hair color.  Second to black hair of course.
0_Apprentice
Is there a reasons so many people have brown hair?
1_Wizard
Well it depends on the level of eumelanin.  If there is more, the hair color will be darker and vice versa.  Brown just happens to be in the middle.
0_Apprentice
Does the color of the hair change anything else about it?