The breed of dog known for its distinctive blue-black tongue is the Chow Chow. This unique characteristic sets them apart from most other dog breeds, which typically have pink tongues. Chow Chows are recognized for their bear-like appearance, thick fur, and aloof temperament. They are an ancient breed from China, historically serving as companions and hunting dogs. Their blue-black tongue is a result of genetic pigmentation, and while it's a fun fact, it is also used to identify purebred Chow Chows. They are known for being loyal yet independent, requiring early socialization and training to become well-mannered pets.