So far, nobody who has actually done anything more than use chalk dust has come forward and said anything and, since I am a chemist by trade, I thought I would put some thoughts together about the whole idea of colored smoke from BP rounds. First the disclaimer:
Anyone who tries this stuff is absolutely, completely, totally on their own; I make no promises other than you are likely to get yourself maimed or killed by trying to adulterate time tested black powder loads. If you are willing to disregard your own safety for the sake of impressing the crowds more than you already do with a good healthy load of ffg or fffg powder, be my guest but don’t come crying to me when your new CAS name is “ole one-eye.”
OK. Commercial and a lot of military smoke flares use the same basic chemistry: an oxidizer (potassium nitrate and potassium chlorate are common ones), something to oxidize (sugar, charcoal, etc.) and in some cases a filler to moderate the burn rate. Sawdust is frequently used for this purpose. Any of the basic recipes make the same color smoke we already are getting from our guns; white or very light gray.
The color in smoke flares comes from organic dyes that vaporize when heated. Materials such as para-nitroaniline red, synthetic indigo, auramine etc. are normally added in 15% to 25% by weight to a mixture of an oxidizer and lactose (sugar) which are mixed in a roughly 3/1 ratio. When the flare burns, the organic dye is vaporized and forms very small particles which drift with the white smoke giving it color. In theory, the addition of some quantity of the same organic dyes to black powder loads might,
MIGHT color the smoke from a firearm.
Colored flames from ignition of black powder could be achieved by addition of metal salts which will color a flame as they change oxidization states. Copper and nickel with make green and blue while strontium would give a red/pink flame. This change to the basic yellow/orange color of the flame would only be visible in reduced light.
The problem I have with any of this stuff is you are adding a lot of unknown chemicals to the powder. If you just added an organic dye to the powder would the much faster burn rate of the black powder (as opposed to the sugar/oxidizer mixture) serve to volatilize the dye? Would you have to add some more potassium chlorate to the powder? What would this do to the chamber pressure? There are a lot of questions here that we just need some testing to answer.
If anyone out there has a firearm they can afford to lose and a rig where they can remotely fire it, then maybe you are a candidate for a research project like this.