I started wearing a red helmet & jacket this summer & it helps a whole lot in making people see you. High beam, as Freidman say, is also good.  

Altho not an article of clothing, for increased visibility and noticeability, I run a modulated headlight and light bar on the high beam during daylight hours. On poor lighting conditions such as sundown or tunnels, etc, the modulator automatically shuts off. I also run an LED tail light bulb which lights a series of LEDS in sequence giving the appearance of a rotating light which changes to a flashing light when brakes are applied. A few strips of reflective tapes on the bags also help for vehicles in the rear...the thought being that in a bike/car crash, the bike rider will alway be the first on the scene.""(