I am not sure but I find that weird. My panther is always brighter than can be at night. He is bright yellow and red right now as he is every night. I have never seen him dark ever. Not saying there is anything wrong, just a little strange I guess. I will notice every so often though if the cage is disturbed just ever so slightly he will immeditely start turning from yellow to green even if his eyes are closed the whole time.It is like he senses something going on but does not wake up. Is there anything that could be disturbing his sleeping pattern?