I did some looking and it seems the High Vis yellow and Yellow green are the best, followed by High Vis Orange. Think of what the road workers wear. I also read somewhere that Hot pink is very visable. The blue was also but not as good at night. I also found a site where they were testing what colors colorblind people could see. www.dartmouth.edu/~sullivan/bike/colorbv.html

Basically High Visability colors, reflective tape and lights if you want to be seen.