Leopard Gecko Colour Change

Question
I got my leopard gecko 4 months ago and he was lime green and purple. He shed his skin several times, but he always returned to the same colours once he shed his skin. About two or three weeks ago, he shed his skin, and his lime green skin changed to a definite yellow. The purple seems to be the same. This was the first time he shed his skin since the onset of Spring, but the temperature in the terrarium has remained about the same. Do you know why he has changed colour?

Answer
 Since you have color that is uncommon, a carefully bred color morph, I would suggest contacting a breeder going for those colors.  Sometimes this trait comes from a parent and it's normal, a part of the aging process.  With so many morphs in leopard geckos, I would say that normal aging is probably the reason.