Red can explicitly "mark" a person or monster in such a way that it become obvious what they truly are. The physical mark is usually symbolic (a vampire may have a branding of a cross on their forehead, a werewolf may have a scar shaped like a crescent moon). Completely human sinners are unique in that they receive a stigmata that increases in severity depending on their sins. A petty thief may have welts on his palms and feet, but a serial killer will pour blood from the same places. The physical effect is secondary to the effect of stigmatizing the victim. Normal mortals will be made severely uncomfortable by the presence of the Marked, instinctively sensing the monster that they are. A Hunter will be able to recognize specifically what they are by the same instinct. The effect would be semi-permanent, lasting until it is dispelled by a common counter spell or similar blessing.

Sound okay?