I found this:
Recently I received a call from someone asking about the blue born puppies. That was a real blast from the past. Hadn’t heard of anyone having blue born puppies in some years. When a dog is born blue it is different genes that effects that then the GG genes. The dd gene is what causes this at birth and the Yorkshire Terrier should only be carrying the DD. A blue born puppy will also have self colored pigment, such as blue nose. The DD gene is what allows them to be born Black/Tan. The upper case always means dominant and the lower case always means recessive. This is obviously a deep buried recessive that the animals are carrying that they have passed onto the resulting puppies. The breeds that are born blue are born with the dd gene, but in Yorkshire Terriers this should not be the situation to cause the blue coloring.
Unfortunately with blue born puppies the situation is usually fatal. Very few live beyond the 1st few days. The ones that do survive almost always at the time they would normally break blue, lose all their blue body coat and get a very leathery skin that is like an elephant hide and causes the dog to be in extreme pain. At that time the dog has to be humanely put down. I have heard of a couple that have lived a normal life, but I think there are very few that do. Do not be tempted to raise one of these as you are opening yourself to heartbreak, let alone what the dog will go through later in life. http://members.aol.com/CYorkie/Genet...Chocolate.html