I was at an LEO/Mil only 2-gun match the other day and saw some purple shell casings. I picked one up and made the comment that someone was really moto about marking their brass so no one else takes it. I later found out that the Border Patrol has their practice ammo casings dyed purple so that their guys can tell the difference between practice and duty ammo. I never thought it was hard to look at the bullet and pick the one with the funny looking tip LOL. Gotta love the government.