I'm gonna have to agree.. The information here is all based on heresy and conjecture... Any FAQ about colored flames should be based on actual information, instead of just 'i heard that maybe you'd get this color if you maybe used this stuff'.
Here's a few clarifications you might like, based on actual experience.
Safety: These chemicals aren't universally dangerous. If you want information about inhalation hazards, look up the MSDS for the chemical you are using. In nearly all cases, inhalation of the chemical powder will be worse than inhalation of the burned product. Salts don't turn into a gas, they decompose into their base chemicals. The organic products produced when burning any fuel will be as bad as or worse than most of these chemicals. Also, if you squeeze your wicks out by hand, you should consider getting a pair of gloves. Solvents can let chemicals into your body through your skin, and you don't want to be absorbing these chemicals through your hands if you can help it. That said, the safest are probably the chlorides, sulfates, and acetates and things that don't involve heavy metals such as chromium. When in doubt, read the MSDS, and limit your exposure.
Shoddygoods is right, you shouldn't be putting in as much chemical as possible, you should be putting in as LITTLE as possible to get the desired effect.
Here are some ideas based on things we've actually done:
Fuel: Denatured alcohol.
An aside on fuel... Around the world, people use all sorts of crazy names for fuel. You should, as a rule, ignore whatever crazy crap people are telling you about your fuel, and contact the company that made it, and get an MSDS for the fuel, it will tell you exactly what you are using. Most companies have the MSDS online, and if they don't, they will mail it to you, email it to you, or fax it to you. They are required to do this by most countries laws.
The fuel we are using is Klean-Strip brand Denatured Alcohol, which is about 55% Ethanol, 40% Methanol, and 5% 'misc', Ethyl Acetate, Methyl Isobutyl Ketone, etc. This is a higher concentration of Methanol than most Denatured alcohols. When you are saying what fuel you have used, please tell us what your fuel is made up of, not just the regional name 'meths', 'meth spirits', 'denatured alcohol' etc. Be aware that methanol is fairly toxic before its burned (after which the products are only as bad as anything else you'd burn, if not better, since it burns so clean), so limit your exposure to the vapors, and try to keep it off your skin.
Our fuel burns a pale orangish color with no other chemicals added.
Colors:
Red: Lithium Chloride: about 15 grams per Liter. The fuel may need to be gently heated to aid dissolving, don't heat with an open flame, use an electric heater.
Red: Lithium Acetate: about 25 grams per liter. Dissolved without trouble at room temperature. Color is about the same as the Lithium Chloride, but seems to require higher concentrations. I'm using it because I had a bunch lying around, Lithium chloride might be a better overall solution.
Green: Boric acid: about 22.5 grams per liter works well. Produces a nice pale green. Does not need heat to dissolve in the fuel.
Other colors? Pure speculation. Cupric Sulfate (Copper II Sulfate) does NOT properly dissolve in the alcohol we are using. Copper chloride may give blue, but we need to experiment with it.
If you created other colors, let us know what chemical you used, what fuel (exactly!) you are using, and how much you added to get the desired effect.
We'll have some side by side photos to compare the colors soon. I know this data seems sparse, but I'd rather us have a little bit of good info, than a bunch of speculation. We'll be getting more with time.
A quick note on how to GET these chemicals. Boric Acid is sold as a roach killing powder. Lithium Chloride is sold for firework making and theatrical pyrotechnics, through stores such as:
http://www.iowapyrosupply.com/
Keep in mind that you may have to pay a Hazmat charge to get these shipped to you, and you may be asked to provide ID, and possibly possess a pyrotechnics license, depending on your locality. Your best bet would be to seek out a local theatrical pyro supply store to avoid high shipping costs for hazardous materials. Keep in mind that pyro places will expect you to know at least a little about what you are doing, and sell a whole lot of stuff that you DON'T want to use in poi, so don't just pick up a little of this and that and toss it together, just get what you know you need.
Well, this is only the tip of the iceberg, but I hope it helps.
Peace,
Sam