Mike and I don't know any more about paint formulas than the average person, however, we have extensive experience with using Prussian Blue Dye. CAUTION: If you use this deep blue, very finely divided substance, WATCH OUT! After the container is opened, trying to keep all off this stuff in the proper place is just about impossible. It can be likened to getting a Genie back in the bottle. We used it during the inspection of precision ground aircraft parts as a contact marking agent which shows you what percentage of contact you have after two closely fitting parts are assembled. After using this nasty stuff very, very carefully, we would find little blue spots on our clothing, in our cars, in our homes, just about everywhere. Slightly less authentic cannon carriage paint would certainly be O.K. with everyone we have met who are involved with the creation of authentic cannon. Good luck with your artillery painting!
Regards,
Mike and Tracy