The white ribbon is reflective. I wear it for four reasons:
1. To identify me to motorists. If you're a driver, all bicyclists look pretty much the same. But if you see me with my ribbons once, and then see me again later, you'll know it's me. My theory is that connection -- "Oh, it's the same person I saw earlier!" -- changes me from Just Another Darn Bicyclist Slowing Me Down to a human being.
2. To be eye-catching and reflective when I ride in the dark.
3. To be pretty.

4. To be a wind sock so I always know which way the wind is coming from.