One of them is brown. The other one is reddish. Again, depending on its amount and distribution, one s hair can be yellow, orange, or red. Actually, it is never pure red in the absolute sense, it always has some amount of yellow mixed in, which, technically makes it a shade of orange, but let s not dwell on technicalities. Most people do not have much, if any, of the reddish chemical present in their hair.
All redheads do.
Many redheads also have some amount of the brown melanin in their hair, but not enough to render the red color invisible to human eye, or, rather, mind. A combination of red and brown can produce reddish brown hair, for example. Also, the hair of blonds and brunets may contain some amount of the red chemical. This may produce a golden brown color, or golden blond. Or, the brown color may be strong enough to hide the redness from the human eye altogether.