I am not completely certain what other color pit bull you can breed to get the blue coat, other than blue itself. Before you consider breeding for the blue coat you might want to do some research (if you haven’t already) on some of the hereditary issues that are associated with the Blue coat.
When Breeding Blue Coat Pitbulls What Other Color Pitbull Can You Breed With To Make More Blue Coat?
If you want to get a darker blue coat,breed blue with black,that will some times make the coats darker.
Blues are not a dilution of black color as some would say . Reds mixed with blacks(coats that is) can throw blues, can I say, blues of corse will throw blues but also can throw reds and blacks