I've noticed (particularly in my spotted pythons) that they do get a blueish sheen to their skin when they are approaching a skin shed. From what I've read, I believe it's a fluid they secrete between their top and second layers of skin to aid in the shedding process. Could be wrong, but that's my understanding of it.
Also, my olive has a definite blue tinge to the eyes as well, shen he's about to shed his skin :
http://www.aussiepythons.com/modules...view_photo.php 
