[mgerber]

We have used those in the past with very good results, and plan on reusing them next year. They work like a charm- bright, easy to control, cheap, and quick to set up. My favorite aspect of ring shaped LEDs is that they nest inside each other, which makes it very easy to add on another layer while still keeping the camera in the center.
As for color, I'd think that you'd want to go with something that isn't going to be the same as any background lighting. Green works well, when we played around with our camera settings we were able to get an image that saw most artificial light as orange or red, while the target remained bright green. That makes for much better vision processing.