I've never actually seen one before

This is a gray tree frog that was, oddly, hanging out on a railing at the Penland Gallery. There are two species of gray tree frog, which are hard to tell apart. One of them, the eastern gray tree frog (hyla versicolor), can change colors for camouflage. They have sticky disks on their toes and can climb up glass. Although they are cold blooded, they produce glycerol in the winter which allows them to withstand low temperatures without their cells freezing. These are not the spring peepers--that's a different species of tree frog.