Breeding blue with red crayfish

It depends if they are the same species. There are thousands of species of freshwater crayfish, and they will most likely only breed if they are the same species. They could be colour morphs of the same species, but if they are different species, especially a completely different genus, then it is highly unlikely that they will breed. You could give it a try though, just make sure the tank is fairly large and there are plenty of hiding spots, as crays are often very territorial. Also age will play a part in whether they breed or not. If they are the same species and don't breed, they could just yet be too young. Cheers, Jim