Usually it's funny test new ways to obtain some results.
I've two Canon 580EX flashes and I'm already comfortable with coloured filters which fit under the plastic flap. Anyway since I though up a way to make a filter from a commonly used tool, I wish to show you this brain-child.
I bought these silicone molds for about 1$ each. They're of the right size to fit on a common flash for photography. And furthermore silicone lets light passing through with a nice coloured effect.