What color is the paper of traditional firecrackers?

Gun paper usually contains phosphorus and sulfur, their compounds and nitrates, low and unstable ignition point, and some sand grains. When you break it, the compound inside will rub against the sand, and because of the instability of nitrate, it will decompose to produce gas. Originally, the interior of the gun was closed, and a large amount of gas was generated in an instant, causing an explosion.