I really liked this Instructable:
We put that all together in one afternoon for 2 bikes, with blue LEDs. We idiots didn’t consider that blue lights are forbidden on bicycles too, so now we have to redo it with orange lights if we want to use our bikes on the streets. And at the moment the weather is still to bad and the mood not there to do it again. What a pity, it really is improving your visibility on the street at night.