I am no expert on Biewers or Yorkies, but it looks like your Biewer is just clearning black to tan. Brody had black tips on his tan...which was pale platinum blond...at 14 months, and Mia, who cleared and lost all her black and is now golden all over with no blue, still has black tips on her tan at 2 years old.
One thing I AM an authority on is cuteness...and that is ONE CUTE BABY!