The Yorkshire Terrier is one of the smallest dog breed of terrier type, and of any dog breed. The breed developed during the 19th century in Yorkshire, England. The AKC registration form for Yorkshire Terriers allows for four choices: blue and tan, blue and gold, black and tan, black and gold. Colour alone will not affect whether or not a dog is a good companion and pet. Colour alone will not affect whether or not a dog is a good companion and pet. Even though off-coloured Yorkshire Terriers are advertised at premium prices, being of an unusual or atypical colour is stated to be neither new, desirable, nor exotic. Yorkies and other small dog breeds may have problems if the deciduous or baby teeth do not fall out as the permanent or adult teeth grow. This is caused by the new teeth not growing right underneath the deciduous teeth.