Pleasantville effect in FCP or Color?

I have a tight deadline (May 10) for work, and I have to make a 3-5 minute video using the "Pleasantville" effect- essentially certain people/things in the shot have to be color in a black & white world. I have read up on doing the pleasantville effect in FCP, and have tried it, but the objects I'm trying to keep in color are not uniform so I have been making mattes and tracking them through the shot. Only problem is, you can see the edges of the mattes on the final image even if I feather them a little.

I wondered what the best way to do this effect is - I know in Color there's a way to do it but I'm worried about the time it will take and the learning curve since I don't really know Color.. Could someone out there suggest the best way to do this effect given my time constraints? Any tricks for making edges of mattes disappear?

Thanks!
Grace

There is a bit of a steep drop into Color - it's a fully featured outfit and not really for the dabbler with no time.

What I would suggest is doing the Pleasantville trick in FCP and using keyframes to track the colour changes over time. Mattes shouldn't be required.