My Green Tree Frogs have recently bred, and I will be damed if I know which ones are the males and females.
As for the nuptial pads......hmmm....never found those!!! I looked and looked but saw nothing. On the otherhand, I have a White Lip Green Tree Frog and he has been croaking and croaking calling for a partner (Unfortunatly I only have the male), anyway, he HAS developed darker pads on his feet.
The only thing I can say for sure, was that my Green Tree Frogs got right into croaking when it was time to mate....they would sit on a rock and croak for Hours....and this went on for a good week or so. Eventually the female gave in. I think (only think ) that my female is the larger of the frogs??
But look, I am not expert on the subject, just sharing my experience.