Alma tells us the apostate Amlicites "had marked themselves with red in their foreheads after the manner of the Lamanites; nevertheless they had not shorn their heads like unto the Lamanites" (Alma 3:4). Though we are not told why the Lamanites so marked their own foreheads, Alma does consider the mark as the sign of a (self-imposed) curse.
So why a mark of red as register for cursing? Alma does not call up such an idea from his inner consciousness; it is cultural. In the system of signs by which the Nephites order their universe, red connotes cursing.
That same semiotic tie famously appears in Egyptian books and art. Red is both the color of Seth, the god who confronts the civilized order of things, and also the color of all that pertains to him, including the desert wastes. All that is evil, all that is cursed, that is fit to be burned, trampled, or destroyed takes on a taint of red. We also recall the dot of red ink sometimes placed in the amulet of the Wedjat-eye (and so, at the forehead) in order to subsume, and thus ward off, evil.
There are several words for red in Egyptian, the two most common of which are dashrut (dshr) and timas or chimas (tms). The color word timas concretely derives from the substance of red ink. The names of the cursed (that is, the rebellious) are recorded in (lit. "cut into") a register of timasaw or tms.w (the book of damnation, of the "red ones"). The idea comes close to the idea of marking (by cutting or painting) the forehead with red. Those so recorded ("those of tms.w") are consigned to slaughter by knife and fire (red flames) in the Netherworld. It is the very act of cutting or painting forehead or register of tms.w that activates or "fulfills" the curse: "I will set a mark upon him that fighteth against thee and thy seed" (v. 16). And for Alma the supreme irony is that "they set the mark upon themselves, yea, even a mark of red upon their foreheads" (v. 13). It's all self-applied, and judgment immediately works its due.
The idea, as a whole, is captured in the Egyptian hieroglyph of enemy, a sign which reveals the fate of the Sethian enemy of order and reason--an ax to the head. The sign ironically shows the enemy putting the ax to his own head. Thus for Alma, as for the Egyptians, enmity and rebellion (that is, coming out "in open rebellion against God," v. 18) make up the essence of folly. The curse follows forthwith ("therefore it was expedient that the curse should fall upon them," v. 18). So the Amlicites fall in battle, only to be later identified and counted by means of their red marks. All this again recalls the Egyptian notion of tallying the record of timasaw (tms.w), a tally of accountability and the accounting of fate.
The books of Alma and Helaman have much to say about the doctrine of restoration, that is to say, divine retribution. The doctrine accords with the Egyptian texts that speak of the punishment of timasaw (Book of the Amduat; Book of Gates), as a coursing from "red things" (evil deeds) to "red things" (evil punishments). Alma sums things up with impeccable Egyptian logic (as found everywhere in the Book of Mormon): "Now I would that ye should see that they brought upon themselves the curse; and even so doth every man that is cursed bring upon himself his own condemnation" (v. 19). Like the Egyptians, Alma (as shown again and again in his long book) considers rebellion the worst of all possible crimes--and, as suits the crime, punishment begins its work with inexorable immediacy.