The Golddust Biewer Terrier or Golddust Yorkshire Terrier is a color mutation of the Biewer Terrier. The mutation of Golddust Yorkshire Terriers is, that eumelanin (black-brown pigment) is formed, but not embedded in the coat, so that only the pheomelanin (red-yellow pigment) is visible as a gold tone on the the pigmented parts.
After a while all white-gold Biewer Yorkshire Terrier were banned from the clubs and registries because the white-gold color did not correspond to the standard of the Biewer Yorkshire Terrier which described a tri-colored coat. Pedigrees were changed and all white-gold colored Biewer Yorkshire Terriers were listed as blue-white-gold which made it impossible to find the Golddust Biewer Yorkies. Many Biewer Terriers are still carriers of the gold gene and if 2 of these gold carries are bred to each other, they will produce Gold Dust Biewer Terriers. If both parents are Biewer Terriers that carry the gold gene, you can have Goldudst Puppies and Standard Biewer Puppies in the same litter.
The gold colored Biewer Terrier is not accepted with the American Kennel Club. As of 2016 there are 3 accepted colors for the Biewer Terrier. Black-White-Gold, Blue-White-Gold and Chocolate-White-Gold.
You can read about the chocolate colored Biewer Terrier here.