I was referring more to their eyes and skin. Obviously those in contact with the Naaru seem to change. Could be that their goals are to 'purify' everything that doesn't agree with their morality.
Just food for thought. It'd be nice if something seemingly good ended up being bad in the end.
Also note I used 'corrupting' instead of corrupting. Corruption might not be the word for it, what I'm suggesting is that being in contact with the light for long periods of time affects someone physically and mentally.