Blue born pups - most of them can also not live to maturity. So this is a huge health risk. You do not want a blue born.
Black and tan yorkies (that are black and tan as adults) usually are your woolies. I have one that I got many years ago as a pet and is neutered. I would never want to breed him, since he is not to standard. My feeling is - if you cannot show them, why breed them??
One should want to uphold the standard and to do right by the breed. Breeding is a very serious science and not to be dabbled in lightly without knowing what you are doing - reason you need educated mentors to teach you. Some mentors are good and some are not. So when choosing a mentor, one needs to choose wisely.