Brian,
I think I've told you before that I keep darts. One of the biggest efforts that go into keeping darts is culturing flies, which you already have down. So you're half way there already. If you like blue then azureus are the way to go, although they have don't have a loud call. If you want a frog with a nice loud call I would go with leucs.
Right now I'm working with: Azureus, Orange terribilis, mint terribilis, yellow bicolor, luecomelas, and red amizonicus.
I have some frogs availiable right now, and more tads in the water ready soon. You have my email, hit me up.