In the history of the Fell terrier, which is where the patt blood came from there has been white terriers, bull blood, bedlington and border blood added. The old breeders didn't care as long as it grafted, so with a gene pool like that there is always the chance that years later a white will be thrown. My own pup is one of those, if she was Black and Tan she would easily pass as a lakie, black as a patt. She is to all intents a white fell but everyone calls her a Russell.
At 14 months old, I don't care what colour she is as long as she starts grafting this season or next. Only thing I will