From Peterborough Today. The city of Peterborough in the UK will launch a "Be Safe Be Seen" campaign by handing out flourescent freebies for cyclists and walkers.
“For best all round protection, people should wear clothes or safety accessories that combine fluorescent colours with reflective material.”
Flourescent colors work well in daylight and dusk. At night, light colors and reflective materials are good.
I also use plenty of active lighting on my bike, including a white blinkie on my helmet to catch the attention of whomever I look at, red lights on the back, white lights on the front, and a yellow Xenon strobe mounted on my messenger bag strap up high at my shoulder for the heavy urban cross traffic I ride through.
My goal is to be mistaken for a construction zone. The danger, of course, is that impaired drivers will focus on me and drive straight into me, but that risk is probably lower than that of the invisible cyclist.