Like I said previously, if you've been working with a line of rats for an extended period, chances are you are safe to breed those rats without any issues. Unless you've just been being selective about breeding.
But to point out something, I used to order from Rodent Pro and never saw any high whites. They mostly had hooded, self, berkshire, albino, etc. All safe, non-risk animals.
I actually just had to look up Ralph Davis and watch his video, and I also didn't see any high whites in his colony either. Most strict feeder breeders aren't breeding for colors and strictly go for the healthiest producers they can. Some breed dually as a side hobby and dinker with colors though and never have any issues, even working with potentially high white animals. Then again, I've seen some that started out with a few high whites and have megacolon hit and have to replace a majority of their breeders. It's a roll of the dice.
If you are careful and selective, you shouldn't have a problem even from the potentially high whites you have in your colony. I would suggest reading up on genetics though. It will help you identify possible problem animals.