According to AKC standard:
Colors
Puppies are born black and tan and are normally darker in body color, showing an intermingling of black hair in the tan until they are matured. Color of hair on body and richness of tan on head and legs are of prime importance in adult dogs, to which the following color requirements apply:
Blue: Is a dark steel-blue, not a silver-blue and not mingled with fawn, bronzy or black hairs.
Tan: All tan hair is darker at the roots than in the middle, shading to still lighter tan at the tips. There should be no sooty or black hair intermingled with any of the tan.
Color on Body
The blue extends over the body from back of neck to root of tail. Hair on tail is a darker blue, especially at end of tail.
Headfall
A rich golden tan, deeper in color at sides of head, at ear roots and on the muzzle, with ears a deep rich tan. Tan color should not extend down on back of neck.
Chest and Legs
A bright, rich tan, not extending above the elbow on the forelegs nor above the stifle on the hind legs.
Anything deviating from this standard would be considered a fault.
Alot of people claim to have "rare" dogs, that are actually not of the standard for the breed. The claim this and then attempt to sell them at outrages prices. Please don't fall for a scam. Get a puppy from a reputable breeder who knows what they are doing. You can find a reputable breeder by going through the parent group for yorkies:
Yorkshire Terrier Club of America
Also, don't fall for the so called mini-yorkies. There are not such thing. Yorkies bred to be extremely tiny are not from a reputable breeder and you may experience nothing but health problems.
Good luck!
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Melody/PHFasDog
Email me at PHFasDog

My furkids:
Shadow, Jadzia and Lyta.
Kira waiting at the bridge.
Dogs come into our lives, and too quickly go leaving pawprints on our hearts, and we will never be quite the same again.