Back when I had Green Tree Frogs, they would always sit on a vertical branch and peer down at the ground.
I'm not sure which species of Gray I have, as we have both in Minnesota, but I did find this one and several of the others in the grass on the side of a trail next to a small pond surrounded by a young small forest and fields of prairie land. He also lacks dark black outlines on his grey bands, so I suspect that he may be Hyla chrysoscelis.
They sure are neat and interesting little frogs, and they seem very popular on this board.