Alma 3:5
The Lamanites did not respect their bodies enough to cover them. They wore armor into battle, but normally hey were almost entirely naked. They shaved their heads and when they went into battle, if not at other times as well, they marked heir foreheads with red. The skin of the Lamanites was dark because of the curse that their fathers had received because of their unrighteousness. They had rebelled against their brethren and had tried to kill Nephi because he was a just and holy man. Their posterity now carry that curse in their curse.