Thanks for the welcome and the good advice for frog ID, folks. Turns out that the lime-green froglets now climbing all over the emergent plants in my pond are, in fact, newly morphed gray tree frogs--at least according to the photos I've been able to dredge up online. What amazes me, however, is how a froglet that's still swimming around in the water goes from a mottled brown to the beautiful green so quickly. Makes sense, though, considering the fact that brown protects them in the pond and green protects them when they crawl out.