There is no black hair in it More probably, there is no yellow hair in it.
Related Commentaries of Leviticus 13:31
Leviticus 13:31
31 And if the priest look on the plague of the scall, and, behold, it be not in sight deeper than the skin, and that there is no black hair in it; then the priest shall shut up him that hath the plague of the scall seven days: