I would just say mixed breed because my rabbit looks just like that and she is a Dutch mixed with a mixed breed. Mine is even very close to looking like American Chinchilla weight and all, but I know she isn't cause I'm the one who bred her parents. Wouldn't it be so much easier if they had those DNA things like they do for dogs?
Her color is chinchilla but unlikely she’s a purebred american chinchilla especially if you got her from a pet store as those are quite large rabbits and their max weights are 12lbs. Chinchilla as a color is recognized in a lot of different rabbit breeds. The standard chin is a 7.5lb rabbit so if anything I would possibly a mix of that