Different styles of armor worn by Sahtan military, city militia/law enforcement, Church guards, and guards of the Imperial Isle, in Vattu.
more details why not: the military preserves a more thorough and tough form of the armor that’s not used elsewhere. Red has been the signifying color for the Empire since its inception, signifying the Mortal Aspect of Tarrus, the allegorical figure of the Emperor himself. The shield carried by guards of the Isle signifies more explicitly the theology underlying Sahta’s notion of leadership (more here). The city militia wear cheaper simpler armor, and the black enamel isn’t meant to be significant in the same way I don’t think. The Church guards wear white (the color of the Righteous Aspect), as do all Church personnel, and their armor is of an older and more ornamental mode.
