This is something I keep finding myself doing. Switching the camera to a long exposure, something like 1 or 2 seconds, and then shaking it at some lights, usually in the dark. Click on the image for a larger picture.
It's only got two colours:
A long exposure with some colour film gives these fireworks some abstract trails. There's some more HERE. Travel theme
The sum total of my attempts to take photos of lights out of focus: In this last one, I'm trying to contrast the modern structure of light and glass with the old steel Victorian bridge in the background, which you can just see in the centre of the picture: