Raintree Fusion - Fireworks - Changing Materials

You are looking up at the dark sky. Boom! There is a huge explosion. Crack! Red and orange fire explodes above you. Whiz! The sky is filled with light, colour, and sound.
You are at a fantastic fireworks display. You wait for the next explosion.
Do you know fireworks come in different colours? What makes them burst at just the right moment?