Copper and barium need a real abundance of chlorine, even when no metallic fuels are involved. Really good compositions have >25% chlorine in them all in all. For green you only need barium chlorate and a resin fuel, shellac or red gum. Barium chlorate forms barium chloride when decomposed, with twice as many chlorine ions as needed, since it's the monochloride that emits the green light. Copper needs either ammonium perchlorate or potassium chlorate and perchlorate with "secondary" chlorine donors, usually PVC and parlon. Copper chlorate or perchlorate can be used, but they are dangerous, since they are primary explosives and not "pure" chlorate/perchlorate but complexes with ammonia involved. Strontium needs the least chlorine. Without any chlorine, strontium salts burn to form strontium hydroxide, which emits orange light. It's enough to add so much chlorine that 25-30% of the strontium forms strontium chloride. Also here the chlorate and perchlorate are almost impossible to use but in this case due to hygroscopicity. The military uses strontium chlorate and perchlorate in some signal rockets, though.