A dog with a black tongue is not necessarily the best, because the dog's breed, personality, health and other factors will affect whether it is suitable as a pet or working dog. Tongue color is only an external characteristic of a dog and cannot be used as the only criterion for evaluating the quality of a dog.

Some breeds of dogs are born with black tongues, such as Chow Chow, Shar Pei, black tongue native dog, etc. The dark tongues of these breeds of dogs are one of their characteristics and are associated with purebred appearance. However, tongue color is not the only factor that determines the purity or quality of a dog breed. There are other factors that need to be considered, such as size, appearance, personality, behavior, etc.

In addition, tongue color may also be related to the dog's health. If the color of your dog's tongue suddenly changes, or other abnormal symptoms occur, such as difficulty breathing, loss of appetite, etc., you need to take your dog to the veterinarian in time to determine whether there is a health problem.