Well, the absolute lightest and truest silvery grey and stark black Axanthic I've ever seen is the Lightning Pied. http://www.worldofballpythons.com/morphs/axanthic-pied/
So far, even as adults, they are that same pale silvery grey and deep black. Of course, they also carry a pretty good price tag, but mmmmmm are they beautiful. I got to see one in person at my last reptile show, and I like them even more in person.
Gale