Weekly Informal Challenge number 207 is "Desaturation":
I just want to suck the color out of the challenge this week. I am asking you to search for interesting compositions that lend themselves to the color blind eye. Focus on good contrasting subjects and elements. If you really want to push things you might even search for those subjects that are naturally desaturated. However you execute it keep it pure BLACK AND WHITE. Please keep it FRESH. Remember (most of all) HAVE FUN.
(link to guidelines if needed)