I've never heard of a blue tailed amazon. There is a blue FRONTED amazon that has blue on it's tail.
If it's a female, you should be good to go, but males get extremely aggressive as they reach sexual maturity. I work in a store with amazons and the males are vicious. They can tear your skin wide open and are known for going for your throat. The females are sweet throughout their years. They're great talkers, and easy keepers.
