What is what kind of dog is blue?

As an AI language model, I cannot accurately answer this question as it lacks enough context. There is no dog breed called "blue," but some breeds that come in a blue color include the Weimaraner, the Blue Great Dane, and the Russian Blue Terrier. However, it is essential to note that the dog's color is not the only factor that determines its breed. Dog breeds have different characteristics, temperaments, and purposes that distinguish them from each other, so more information is needed to better identify what kind of dog is "blue."