How I did this:

I used what I call a "whirlygig:" one of those battery-powered toys that lights up and spins...you might get one at the circus or the fair. I suspended it from a stand, turned it on, and the spinning motion caused the toy to wobble on its string.

I then turned out the lights and experimented with shooting the spinning device at various shutter speeds. I also changed angles and distance, to varying results. It was fascinating to see the different patterns and color combinations I got from a simple array of red, yellow and blue LEDs.