I think that for the most part, chitons are algae eaters, but as you mentioned, its not common to see the colors that this one has. I'd keep an eye out just to be safe. Even if it did start eating corals, I don't know how you'd get it off the rock.
well i havnt seen it in a few days and all corals seem fine but i will keep a eye on things and maby get some more close up pics when i do see it again...