Yorkies are dark silver blue and tan, they should not bee black/tan except when they are puppies.
Yorkshire Terrier puppies are Black and tan, but then they loose theyre black color and get this beautiful dark silver blue color
Just read the standard:
American Kennel Club - Yorkshire Terrier
Yorkies are just in this one color, they should not be with much white markings (like biewer yorkies, they are just Maltese/yorkie mixes i think, theyre not pure yorkies).