I've only seen information about brightness, and it appears that white is the brightest. See:
Which Retro Reflective Tape Is The Brightest ? | Retro Reflective Tape | Retro Reflective Tape
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A conclusion is the place where you got tired of thinking. - S. Wright
Favorite rides in the stable: Indy Fab CJ Ti - Colnago MXL - S-Works Roubaix - Habanero Team Issue - Jamis Eclipse carbon/831