I believe the blue frog is a female. However I'm not sure on the size of the frog from the pictures. So, I don't know if she is sexually mature. But aside from croaking, males have much larger tympanic membranes (ears). They will be bigger than the eye. On a female it will be the same size or smaller than the eye. That's the easiest way to tell.

I don't know if you know much about genetics but if this gene is recessive like I think. Then breeding to a normal will produce all normal babies (unless the other parent is carrying the "Blue" gene) that are Hetrozygous for the "Blue" gene. This means if you breed siblings or back to the blue parent you will get "Blue" babies and normal babies.
If you don't want to inbreed a lot then the only way you can do it is by doing several breedings and then breeding the half siblings together. Het to het breedings will produce a lower chance of having "Blue" babies though. You then can continue out crossing and then breeding back in order to prevent weak genetics due to inbreeding.

Sorry if you already know all that. I breed snakes and find genetics fascinating.