It is that burn chemical compound include specific element, flame up it with peculiar color of each element. The star of fireworks can been done by mixing chiefly three powder. It is a combustion material which promotes the oxidant and combustion by which the medicine and oxygen by which the color is put out are supplied. This is an example of chemicals as a color former.
Recent stars show a tendency to more brighter than usual by using magnesium's etc.
It has been achieved by mixing magnesium's etc,slight neutral tints like difficult pink and purple, etc. This change based on structure of changing color star like left figure. It is concentric sphere consist of some layers of powder which burn another color each other. Put standard materials like a rape seed or ceramics grain in center, and coat powder over it again and again in due order. Spread and dry up them over drying table under the sun whenever one powder layer grow little thick.