Leviticus 13:2

אָדָם כִּי יִהְיֶה בְעוֹר בְּשָׂרוֹ שְׂאֵת אוֹ סַפַּחַת אוֹ בַהֶרֶת וְהָיָה בְעוֹר בְּשָׂרוֹ לְנֶגַע צָרָעַת וְהוּבָא אֶל אַהֲרֹן הַכֹּהֵן אוֹ אֶל אַחַד מִבָּנָיו הַכֹּהֲנִים

When a man shall have in the skin of his flesh a rising, a scab, or a bright spot, and it becomes the plague of leprosy in the skin of his flesh, then he shall be brought to Aaron the priest or to one of his sons, the priests.

The Jews in the wilderness had Middle Eastern olive complexions. They were neither Caucasian nor black; they were somewhere in between. The Mishnah in Negaim (2:1) discusses how to properly evaluate signs of tzaraas (usually translated “leprosy,” but really a spiritual affliction) in Jews of other skin tones.