Never heard that before, could not even see it being enforced. If I get a dummy 1919 from CA. or a state that requires red on the end of a barrel, it is coming off when it gets here. NC does not require it. That is why I do not think it is a fed. law, I think it is at state level.
As far as putting a red tip on the end of your barrel of a real gun, every blank adapter I saw in the Military was red and went on the end of a real gun. So, once again, maybe some thing at the state level.
But, I am open minded, so if some one has proof, this would be a great to know.
One of the few, Frank