A juvenile American tree frog (Hyla cinerea) of unknown age was presented to the Exotic Service at the Tufts University School of Veterinary Medicine for an acute onset of swelling of the left ...

Coloration of the frog is Green/Gray depending on lighting and seemingly what the frog happens to be sitting on. Answer: It is a juvenile Gray Treefrog. They can be as small as a fingernail or so.