Memorial Ride

+1, I was about to suggest doing your bikes white as well.

I know a friend in America, that when his best friend passed away due to a driver DUI with a lorry, he put up a white (sprayed) bike where he passed away. Probably illegal to do it here, but it would definitely make an impact if you're all in white

Its been done several times here, if you ride/walk around holborn, clerkenwell, Dalston and a few other places there are several ghost bikes in memorial to our fellow cyclists that have had their lives cut short.