Conti website (and others) say the black GP4000 is the same as GP4000s (except graphics as Carleton pointed out).

Don't bother to get the colored GP4000 unless you are stupid like me and think it would be cool to have colored tires. The thing is I had these blue GP4000 sitting around a year until I mounted them, but now they're on a different bike than originally intended and the colors don't match. Also, the color down the middle of the tread seemed to rub away after one or two rides anyhow (at least on the ones I have).