Gray treefrogs are able to change their color from gray to green based upon their immediate environment. The common gray treefrog (Hyla versicolor) found in more northern climes is not found in my region of Kentucky though it is physically indistinguishable from the Cope's gray treefrog. They can be distinguished by their calls, with the Cope's gray treefrog being shorter and faster. And quite interesting is the fact that the common grey treefrog has an extra set of chromosomes, which means that the two species can not hybridize.
