I wonder if the figures in the frieze, below, were originally outlined in white, or if that is just part of the restoration process. I don't know much about the art of that era (500-ish, I suppose you could say "late antiquity Roman").
No, the outlines in white are not original but part of the restoration. I’m an Art Historian, and my specialty is late Antiquity (100 AD - 500 AD) and early Medieval (500 AD - 1000 AD).