Oh, and you asked the little boy being a carrier. Based on the litter you produced, BOTH parents have to be carriers to get a parti baby. So the regular yorkie puppy has a 50% chance of being a carrier and a 25% chance of being a standard.
single allele genetics is quite easy when using a punett square. I drew a picture of each one in Pine Haven's explanation for every one to see. She was right, but i have to disagree on her carrier Vs. standard scenario.
an explanation of my drawing for those who don't know. "R" is the dominant gene of standard coloring. "r" is the recessive piebald gene. To get a dominant standard color without being a carrier you need "RR". To be a carrier you need "Rr" and to be a parti you need "rr". the only was recessive genes are ever shown is if they are double recessive "rr". the other letters in my drawing should be easy enough to figure out (s- standard, c-carrier, and p-parti). i hope this helps.