They work by shut up and watch that’s how.

Fireworks work by igniting metals and salts using gunpowder. All those components should work in a vacuum.

Usually the propellant and other combustion materials will include an oxidizer, so an atmosphere really isn’t required.

I don’t know how the Cardassians would do it, but Starfleet would just put colored gunpowder in a torpedo casing.

How come the Sun stays lit even though there’s no oxygen in space? O.o