I say firework-type because you can also make flowers from them or if you use fall-ish colors, they can be great turkey tails or cut out for fall leaves.
All you need is...
They do need to be washable markers in order to get the right effect.
You flatten a coffee filter, fold it in half and continue to fold the cone shape in half until it gets small. (Think folding like you do for snowflakes only using a coffee filter.)
Then you take a rubber band and wrap it around the coffee filter in different locations and tightness. It will look like this after you have folded and wrapped the rubber band.
The next step you can see started in the above picture. You start coloring in all the different sections in whatever color you choose. It will look like this.
Next, you stick it in a cup of water or run it under a facet for a few seconds and then squeeze out the excess. Remove the rubber band and...
It's tie-dye fireworks!!