[jmartin]

Ideally, hue wouldn't change too much, but under white lights vs yellow lights etc, I think it would vary some. And auto white balance or auto exposure can really screw with this kind of thresholding.

Anyway, our team has a blue ball. If I get a chance to find a good range, I'll try to remember to post it here. Can't promise it would be anytime soon -- we have a lot of other things to get working first.