White is my favorite color for being seen in situations like this, which is almost every ride. It's common easy to find color of clothing, doesn't clash too much with any other color, highly visible, cool, simple, does its job well. What's not to like? It gets dirty easily, but other than that, perfect.

It doesn't hurt either to have a nice brisk cadence either, for absolute maximum visibility. Every little thing you can do will help.