Puzzle #157: Dogged

You should not have done it (whatever it was), and now, you are being tracked by dogs. It is hard to see in the dim moonlight, but you know that three of the dogs have white in their fur, three have black, and three have grey with each dog having at least one of the colours of fur. If at least one dog has solid white fur, and at least one dog has all three colours in his fur, what are the minimum and maximum numbers of dogs tracking you?

Submit your answer to Gene Wirchenko <genew@telus.net>. Your answer should be in the form of a proof. That means to show how your answer must be correct. The deadline is Wednesday, June 8, 2016 at noon Pacific Time. I will post the answer shortly after.