The Louis Garneau one they sell at Nashbar is bright yellow, with reflective accents in green or something (seeing color is not my strongest suit), and it's pretty cheap. I use one all the time, only take it off when it's really hot out. In fact it's getting pretty trashed, so on my last order I got two more, just in case.
I've had a black Louis Garneau for years and it is still like new. It requires four hands to put it on, but once on, it works like a charm. I leave it on all winter to block the helmet vents.