This is from Debbie @ MySpace.com

Removing all the colours except one using Final Cut Pro

How I've done it is to use 2 layers of the same footage on your timeline. The bottom layer you leave totally normal - this is going to be your colour The top layer, you use "chroma keyer" to pick out the colour you want to "keep", and make sure it's a fairly soft key out. Then you desaturate that layer and make it b&w So basically what you're doing is you're making a black & white layer on top of your normal colour layer that has the colour you want keyed out (masked off), so the colour comes from underneath.