Pleasantville/Sin City effect with two colours?

Hey COW's,
Creating the 'Pleasantville' effect in Color is really easy, except the only problem Im having is isolating more then one colour. Would someone please be able to explain how to do this? Or if its even possible?

Thanks alot!

For those who dont know the effect, here is an example of it below. (except only isolating one colour)

Broadcast 2000 "get up and go" Full from Jordan Clarke on Vimeo.

Trent Whittington - Currently studying Associate Degree in Digital Television

iMac - 24inch 3.06Ghz, FC STUDIO 2, Adobe Production Premium CS4.
Asus eee - 8.9inch 1.6Ghz 1Gb Ram, Windows XP