Back crossing to the parents will restore purity, plus the new color you want. As in parent, I mean the purebred mother to second generation son.
You can also take 2nd generation daughter, & breed to a purebred unrelated cock.
Breeding Barred male to solid female will produce all Barred offspring since he's double barred.
Since the male offspring from the first crossing will only be single Barred, you breed them together to lock in the traits you want, & keep the double barring factor of the males.