I did an experiment with my ghosts and it did seem like the green ones were linked to higher humidity. I had 12 in a container that didn't have as much ventilation and constantly higher humidity of those 8 turned green, as opposed to the other batch from the same ooth which had 2 out of 17 turn green. However I did have many unexplained deaths of the greenies. Just thought i'd see if anyone else had this experiance.