Pyrotechnic colorants- reactions & safety concerns regarding making charcoal discs I want to create my own charcoal disks/tablets which will be mainly used for incense and I want each of the charcoal disks to glow different colours (eg one disc glows blue, another glows red etc.). The product will be using charcoal and other ingredients including Arabic gum. I will need to add certain chemicals such as metallic salts and so forth to create the desired aesthetic effects such as the colours.

My main concern is the safety of the product, I would like to experiment to see if any of this will work but most of all, I want to know if the end product will not become a dangerous fire hazard and that it will be non-toxic.
I’ve looked up some of the chemicals online but I want to be sure.
I know that you can add metal salts to flames in bonfires to add a similar effect. 

(Example here: http://tiny.cc/hqjv9y and in fireworks displays. Can I have that similar desired effect with the charcoal disks as well as the safety with it?

Below are some of the chemicals that I’ve found and would like to know if any of them are safe to add to creating my product:


For a blue flame, you want Copper Chloride or Calcium Chloride 
For a light green flame, you want Borax 
For a dark green flame, you want Copper Sulfate or Alum 
For a strong, red flame, you want Strontium Chloride 
For a purple flame, you want Potassium Chloride 
For a pink flame, you want Lithium Chloride 
For an orange flame, you want Sodium Chloride
For a white flame, you want Magnesium Sulfate 


Some chemicals also make coloured sparks, instead of colouring the flame: 


For gold sparks, you want Iron (fillings) 
For silver sparks, you want (powdered) Aluminum


Source here: https://www.quora.com/What-chemicals-can-change-the-color-of-fire

Other sources: https://www.thoughtco.com/how-to-make-colored-fire-p2-602196

Pyrotechnic colorant: https://en.wikipedia.org/wiki/Pyrotechnic_colorant 

https://www.thoughtco.com/how-to-make-colored-sparklers-3980637

https://www.buysparklers.com/product/14-inch-neon-party-sparklers/

I've read that magnesium can be explosive although I also I want to achieve a white hue for one of my discs. Are there any other alternatives for this?

I also would like to add that I may or may not be adding salt peter (potassium nitrate) to the mix. If I do decide to add potassium nitrate, how will each of the selected pyrotechnic colourants behave with it?

I am trying to create a product with as little additives as possible, that burns cleanly, with little to no scent, with hardly any smoke and as mentioned before, is safe and non-toxic.
The best way for you to find out if a chemical is safe for your use case would be to look at the safety data sheets for your chemicals. For your convience, I have linked to relevant ones below. 


Copper (II) Chloride
Calcium Chloride
Borax
Copper (II) Sulfate
Alum
Strontium Chloride
Potassium Chloride
Lithium Chloride
Sodium Chloride
Magnesium Chloride
Aluminium Powder


In general, you will find that most metal salts are acutely toxic. Take for instance, the Copper (II) Chloride, which is noted as having the following hazards, as noted in Section 2.1 Classification of the substance or mixture: 


Acute toxicity, Oral (Category 4), H302
Acute toxicity, Dermal (Category 4), H312
Skin irritation (Category 2), H315
Serious eye damage (Category 1), H318
Acute aquatic toxicity (Category 1), H400
Chronic aquatic toxicity (Category 2), H411


From the same section in the SDS for Aluminum Powder, you will find that it has the following hazards: 


Flammable solids (Category 2), H228
Acute aquatic toxicity (Category 1), H400
Chronic aquatic toxicity (Category 1), H410


You can find out more about these hazards from the EPA GHS Criteria Summary, and the Wikipedia GHS Hazard Statement List.

Overall, you should look over each SDS and make sure that the chemical you are proposing to use is safe for your purposes. 

Cheers