There are numerous reasons for a fish to change colors during the day/night cycle. I'm not sure if you've ever done it (guilty), but, if you have ever left your lights on in your cichlid aquarium for a very extended period of time then you will notice that your males will eventually start to look less colorful, but after a proper day/night cycle you will notice that the color returns. Although, I am not going to go into detail as to why this happens, as it's more than I am willing to type out right now.My Sunshine peacock is pretty bright during the day but at night he seems to get a very pale coloring. I was never worried about it. I assumed this is a natural defence mechanism because some like to hunt others at night and the brighter the color the better a target especialy since they are from a deeper part of the lake with less lighting(in their natural habitat). What would you say AndrewM21?? Would that be one of the possible reasons? That was a total assumption/guess that I never thought to ask about.