Some, I would say most, people like to keep their bike looking like it appeared when first purchased. I am not one of those people but can certainly appreciate people wanting their bikes to look as "factory" as possible.
Reader, commenter, and contributor Raiyn has submitted another project of his, what he calls "Non Dorky" reflectors. The full project is detailed on Bike Forums. In introducing the project Raiyn states:The reason for the double pics is to illustrate what I call the "Stealth Reflector" concept and the use of Reflective tape on the wheels instead of CSPC plastic reflectors. Basically the idea behind the "Stealth Reflector" is to use the same color (or reasonably close) tape as the frame so that it blends during the day, yet provides reflective properties at night.
I did some Googling and came up with a few sites that feature colored reflective tape:FindTape.com