Blue Heeler, or Australian Cattle Dog, makes the best blue dog breeds list. Blue or red coat, with black/tan markings. Solid, mottled, or speckled blue coat, exuding a distinct bluish hue.
Kerry Blue Terrier, one-color breed, curly coat in shades of deep slate to light blue-gray. Muzzle, head, ears, tail, and feet may be darker. Puppies born black
Weimaraners: steely gray with dilute brown coat gene. Some have black dilute gene, becoming dark gray/blue Weimaraners. Blue coat is disqualified in breed shows
Chihuahua, small breed, various coat colors, including rare blue. Solid or combined with tan, white, fawn, or brown markings. Seen in both long-haired and short-haired Chihuahuas.
Bearded Collie: shaggy coat, various colors, including blue. White markings on face, chest, legs, and tail. Body always solid in color, may start with darker coat that lightens as they grow.
Boston Terrier: black-and-white "tuxedo" coat, rare red or blue due to recessive genes. AKC disallows blue coat, but it may show as blue, silver, or gray shade.
Blue Lacy: Rare breed, Texas' state dog. Developed in mid-1800s as rancher's companion and herding dog. Carries recessive blue coat gene, also produces red, cream, or tricolor pups.
Neapolitan Mastiff: Giant blue dog breed with imposing frame and loose, wrinkled skin. Blue coat common, along with black, mahogany, tawny, brindled or striped. AKC accepts blue color.
Chinese Shar-Pei: Known for wrinkles, comes in various colors, including blue. Breed standard allows solid or sable coats. Blue range: light gray-blue to deep slate.
Irish Wolfhounds: Gene for diluting black coat to blue, inherited from the Great Dane. Blue coat with distinctive tint, liver-colored paw pads, nose, and eye rims.