Memorial Ride

A large group of cyclists all in white would present a more striking image I think. Can even wrap a couple of crepe-bandages around your frame (if it isn't raining) to make the bike white too.

A lot of cycling gear is black, so that's quite a normal sight. People dressed all in white is not usual in this country and would stand out more.

It ties in much more with the ghost bikes themselves as well, if the riders are in white.

+1