C. F. Keil and Franz Delitzsch on Leviticus 13:29-31

Lev 13:29-31 Leprosy upon the head or chin. - If the priest saw a mole upon the head or chin of a man or woman, the appearance of which was deeper than the skin, and on which the hair was yellow (צהב golden, reddish, fox-colour) and thin, he was to regard it as נתק. Leprosy on the head or chin is called נתק, probably from נתק to pluck or tear, from its plucking out the hair, or causing it to fall off; like κνήφη, the itch, from κνάω, to itch or scratch, and scabies, from scabere. But if he did not observe these two symptoms, if there was no depression of the skin, and the hair was black and not yellow, he was to shut up the person affected for seven days. In בּו אין שׁחר (Lev 13:31) there is certainly an error of the text: either שׁחר must be retained and אין dropped, or שׁהר must be altered into צהב, according to Lev 13:37. The latter is probably the better of the two.