a great deal of shunning, no respect whatsoever from the rest of the community, and a world of pain from other gecko breeders ;-)
Physiologically speaking - - and I cannot believe that I'm saying this out loud, it's doubtful that anything will really happen. I won't say that it NEVER could, because from a genomics standpoint, too many homozygous recessives thrown together can definitely cause some kind of issue in many species, but in leopard geckos, that hasn't been seen as of yet.
No serious breeders will ever buy your geckos if you mix them up like that, that's the big thing. If you're only breeding to have pets, do whatever you want - but - I'm going to go out on a limb and say that once you get 12 eggs out of a female and they all hatch and surprise, you have 12 "muddy" geckos. They may turn out to be beautiful, who knows - but you're PROBABLY going to want to sell a few of them. And no reasonable person with any desire to breed is going to buy them, case closed.
Dude (Evan and Craig, both of you) - just...don't do it. Leave it alone. Buy geckos from quality breeders so you know what you're getting (Kristi is one of them, for sure) - and if you want to breed those, make sure what you're breeding doesn't muddy the genetic waters even more on the ONSIDE chance you ever want to sell them again.
Kristi, I like your answers, don't feel bad <3
...this guy sums it up pretty well, by the way:
http://www.youtube.com/watch?v=NUWJ8tbfWR0
Give it a gander.