This is a little plugin I just threw together to try it out. It notifies everyone when a player is black and white. I don't really want to own or maintain it so I just thought I'd throw it here and if someone wants to run with it they can make it their own and submit it as a new plugin.
Possible features enhancements include:
Convar to determine if both teams get notified or only survivors.
Include model in the text (example "Madcap (Louis) is black and white.")
Change color of notification.