The Dog-day Cicada exited its nymphal skin at last and clung to the tree trunk, waiting until the wings are fully formed. The green colour is Hemolymph, insect blood (which is yellowish-greenish, not red) pumped into the wings. In a short time the wings will look like this: https://pbase.com/laroseforest/image/127222582

These are not the periodical cicades that emerge in huge numbers every so many years. This species is seen annually, with cicadas emerging singly through the summer and never in any great number, at least up this way.