I have a supposedly normal patterened leopard gecko right now. I bought him revcently from the a local pet store. I noticeed something strange though; during the day I put on a "full spectrum" daylight lamp and after a short while he looked like a tangerine except for his tail which is a gray-brown color. It remains like that for about 15 mins after I take him out of his cage but then it turns a dull brown-orange color. Is this normal or should I be worried?