i think if you speak to one of the many good breeders here.. like Dr Dave, you will learn that the blue is a genetic ressesive gene.. it can occur even if you breed black/black, red/red/ etc. brreeding red with black does not increase chances of blue or even fawn color
It seem that you are very well verse of dobe - just out of curiosity, you must have encouter with dobe for years? I have decided not to have it as it will be problematic in long run. Is not the money but time factor concern.