I gotta agree that snake is very under weight! Not the darkest I've seen, but definantly a beauty. Put some weight on that snake please and keep us updated.
She sure is pretty, i don't think it is a pure red tail but a common columbian cross with a ecuador/longicauda or some other dark boa...
Maybe a melanogaster boa, but i think you cant call it like that... Only if the history of a snake is known and reliable i think you can call it like that...