i saw this video..
http://www.youtube.com/watch?v=TSYMKUtNuw8

and would like to know if anyone has done or knows how this can be done .. id like to give it a shot and it seems very interesting ... but trying to figure out how this was done and if it possible to do in fcp .... anyone has any suggestions?

Are you talking about the pleasantville effect where some parts are color? That's pretty easy to do in FCP with the 3-way color corrector... check out this tutorial:

http://www.lafcpug.org/tutorials/basic_pleasantville_look.html

I've never tried it using more than one color, but you might be able to figure it out. You could also use After Effects or Shake to rotoscope the video and mask certian areas too, but that would definitely take you a lot longer. Cool video though, I liked it