Can a Melanististic leopard male gecko, mate with a tangerine leopard gecko to fertilize its eggs succesfully?

I' had 4our but they're all infertile.
Answers:
They can mate and fertilize eggs in general. The problem may lie with the individuals involved. Male and Female both need to be old enough (18 months at least) but not too old and in good breeding condition (ie. good fat reserves esp. for the female). The first couple clutches a female lays can sometimes be infertile.
After that you need to make sure your set up is good (store bought incubators are best, homemades can be made but take a little more tinkering with). Any mistake in temperature or in transportin the eggs (don't move them around, or tilt them in anyway, this will kill them) can cause an otherwise viable egg to die. Also, never give up on an egg untill it starts to smell or deflates. I've had viable eggs grow mold and still hatch out wee ones.
www.kingsnake.com has a great forum to ask questions.
But why would you want to breed a melanistic to a tangerine. Both are highly line bred to get those individual colours. By mixing them you will be dilluting the gene pool and will likely end up with bland normal type geckos. There is nothing wrong with normal types, I love my girls, but with so many different morphs why not just get another tangerine or melanistic and go from there. If you are intending on selling them you'll get more for them.

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I am not overly familiar with Leopard Geckos, but I can tell you from my experiences with snakes:
Melanistic and Tangerine are skin pigmentations. Although they are mutations, they are very minor genetic alterations that do not link to infertility. However, there are often other health issues which interfere with reproductin, due to heavy inbreeding used to get the recesive genetic traits.
It is very likely that only one in four eggs would survive, and that's assuming they do get fertilized.
If you are well researched about proper Leopard Gecko mating and nesting procedures, then you may have to try several broods before getting viable eggs. If you are not familiar with such practices, then you may be asking the wrong question at this time =)
Good luck!

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color has nothing to do with fertility, age does though, a female can be too young, and males get too old, and there sperm dosent work anymore, your geckos probably werent unfirtile, just too young to breed *sucessfully. they can still breed, but it dosent mean much.