I want to add a color to vapors, like the vapor that comes out of glycerine when heated.
Is there a chemical compound I can put into glycerine that makes the vapor colorful? Or is there a chemical compound over which I can pass the vapors and they get colored?
By means of physics, just vaporise the glycerine and shine light on the vapours -- like it is done for water curtains. Similar results may be achieved with fog machines (here). The advantage: your light source defines when and what kind of colour is visible behind a dark background / in a darker environment. To quote from a lecture by French chemist Hervé This: "Egg white appears only white because of the white light normally used in the kitchen, as soon we use red light it were egg red."
If, on the other hand, you want to use chemical means, mix glycerine, water and appropriate food colours, and evaporate it in a fume machine. A how-to like this may be a good starter.
