The extra heat generated excites the electrons in the colour-producing chemicals added in the firework mixture and thus produces beautiful colours. The oxidising property of potassium chlorate is ...

Red phosphorus is fairly stable, but microscopic amounts convert into dangerously unstable white phosphorus through friction heat ... a stiff paste of potassium chlorate and glue and rolling ...

The heat generated by the burning red phosphorus triggers the decomposition of the potassium chlorate. The oxygen released by potassium chlorate further assists the burning of the red phosphorus.