Search for the 3M stuff. Scotchlite, Scotchbrite....something. Doesn't matter the color of the tape, at least around here--never the first problem with police. I have black tape and it reflects white in headlights. Match your bike so it's not so obvious in the daytime....it will be noticed at night. So long as the car is positioned to see it. Like a mirror the angle of the dangle has to be right for it to reflect back to the light source. A drawback to ANY passive (reflective) lighting system.

Commuter Forum Sticky on the subject.