The United Kingdom Kennel Club do not recognise these colours as being a Pure Bred British Yorkshire terrier. The one's seen on some "Puppy Mill for Sale" sites are being sold by unscrupulous BYB breeders, who have seen the Parti's & Biewer's being sold for big American $$$, and so jumped onto the inevitable band wagon here in the UK, by making up their own little lookey like eees, who unfortunately grow uplooking like Maltese/Shih-Tzu crosses, which is most likely what they are, or Jack Russell crosses, actually any cross with a Yorkie and a white dog seems to be their game. Ask them if their dogs have pedigree certificates to authenticate their true ancestry? and not just their little home made ones or the Dog Lovers Registration or Pet Lovers registration, which alot of Puppy Mill or BYB's use, and you will see they don't have anything credible.
The sad fact is where there is money to be made by exploiting a dog as some how being "rare", you will always get BYB's jumping onto the band wagon in any Country.
Use a little common sence.....do your own research.....
Link to the YTCA:
Yorkshire Terrier Club of America (Awards)