Purebred blue cats also have ring marks on their tails. Many blue cats are born with ring marks on their tails, which may fade or persist as they grow. Blue cats with ring marks on their tails are the most common in the cat world. Atavism cannot be used as a criterion for judging whether a purebred is pure. If you want to observe whether the blue cat breed is pure, you should judge it from many aspects such as body, appearance, genes, bloodline, etc.