I discovered an iPhone App the other day called "ColorSplash" - it lets you convert your pictures to black and white then "paint" back selected areas with their original colour. It's great fun!
I smugly worked out how to do it in Photoshop on these larger pictures - create a duplicate layer, desaturate it, then use the eraser tool to wipe away the desaturated layer and reveal the colour beneath. Merge back the layers when you are done and there you have it!
I'll be popping back to see how you've got on later - no talking at the back East and stop tormenting Scarlet. And remember, the bell is a signal to me, not you.