I've seen a couple people over the last year or so using these multi-colored rear LED lights on bikes. Mostly I've seen them sold on Amazon, Ebay or the cheap Chinese websites. Then again I've seen some of the more expensive / brighter versions being mentioned here on Bike Forums ( although I forget the brand name at the moment ). I don't know what would motivate someone to want something like that on their bike but personally I could care less. What is more concerning to me is that I'm seeing more people use these "Blue LED" lights on automobiles that I KNOW ARE NOT COPS. I had one of those behind as I was driving down the road just the other night ( steady blue light on dashboard, non-flashing ) and when it passed me I could tell it wasn't a cop.