Going back from the end of Myst IV
 

I'd like to do some sightseeing on an old save. Since I had played the game through from start to finish, the save is at the end, right after the door with the color puzzle. As far as I can tell, I'm trapped in there- I can't figure out how to open the door from this side, and the door inside the building is locked. How do I get out?

As far as I can remember, the only way out is to play it through. Which means you can't go back from there.

That's pretty stupid. I guess it's not too harsh a punishment to have to play it again, though. :D