Those are the only suits we see in the film, yes. Clarke's novel has an emergency spacesuit locker in the Centrifuge. Not seen on screen but a probable location for the fifth suit.
As to color, I might imagine the fifth suit to be ORANGE!
The Lunar suits are silver with white helmet and blue packs.
Look at the "charging instruction" on his chest. It's all wonky
Seem also like they use the same pack on both those pictures with the yellow and red suit.
Also A QUESTION Which playboy magasine is that guy holding? in one of the other pictures? Did kubrick make a "future" playboy?
For Peter Hyams' sequel, "2010: the year we make contact," Bowman's red suit was re-created from stills. This suit is a bit bulkier, especially in the shoulders. He doesn't appear with the helmet in the film as I recall, but there are stills of him with it. The chest pack on the repro suit is a lot smaller, and the colors of everything are a bit different.
Dullea with the helmet, from the "2010" DVD package.