You are referring to the Green Cranwelli (C. cranwelli also called the Chacoan Horned Frog) and Green Fantasy frogs. Fantasy Frogs, are infertile hybrids of C. cranwelli and C. cornuta (Surinam Horned Frog). They have pointier horns than C. cranwelli and their hipbones are more distinct. Green Cranwellis don't completely maintain their green color into adulthood. They can be a mix of green, tan, and brown. Fantasy frogs' color may also fade with maturity. The pattern on a fantasy frog's back has connected spots (from the C. cornuta), whereas the C. cranwelli has distinct, seperated spots. Fantasy frogs are harder to come by and cost more because they are a hybrid.