Hm, Carrot would be Blue, Granny Weatherwax Green, and of course Nanny Ogg as a Violet. Yeah, let's see them try to sexy her up. Vimes would pull of the Red/Green combo. And Rincewind would have to have Yellow. And be completely terrified of all of his Corp.
Death would be in charge of the Black Corp, and I'd would be forced to try to join it in anyway possible.