Color shift seems common, but not life threatening from what I've seen. Try to maintain good diversity in what you feed and feed often (at least 3 times per week, preferably more without causing degrading water quality). Light is irrelevant for these animals, so no need to worry about that. Actually, I glanced at that article and that should be plenty of information on them, which goes along the same lines as what I've typed here (I just like to see them fed more often).