Jerry Jackson, a professor at Florida Gulf Coast University, says a blue frog is a rare find indeed. In the face of overwhelming habitat loss and species extinctions, it is truly great to discover something like this, Jackson said in a statement issued by the sanctuary Tuesday. The blue shade is caused by a genetic anomaly, researchers say. The normal color of the green tree frog is produced by overlapping blue and yellow pigments. In this case, yellow is missing. The frog was discovered at Corkscrew.