Hi and welcome!
I think you're very sweet to be concerned and I hope you get all your answers. If I remember correctly, from another thread, parti colored Yorkies are not acknowledged through registration but they do exist because there are people on YT that have them. I'm not sure if a little white on a Yorkie makes them parti or if it's just considered a flaw. I wouldn't even bother with registering them because as I believe you've already learned that CKC isn't the best registration anyway. Sell them to nice pet family homes and just be honest about not being a breeder and about you thinking you could keep them all etc etc.
I cut this from the AKC web-site:
Colors
Puppies are born black and tan and are normally darker in body color, showing an intermingling of black hair in the tan until they are matured. Color of hair on body and richness of tan on head and legs are of prime importance in adult dogs, to which the following color requirements apply: Blue: Is a dark steel-blue, not a silver-blue and not mingled with fawn, bronzy or black hairs. Tan: All tan hair is darker at the roots than in the middle, shading to still lighter tan at the tips. There should be no sooty or black hair intermingled with any of the tan.
Color on Body
The blue extends over the body from back of neck to root of tail. Hair on tail is a darker blue, especially at end of tail.
I could have sworn I read somewhere that a tiny bit of white on the chest as a baby was okay but can't remember where I read it...someone will know better and respond
Good luck!!