Ceiling colors?

Hit "tab". It removes all the UI and it allows more flexibility for moving the camera around. While in that mode you can use Q key to get really low angles for example, and you can move the camera outside of the boundaries where your sim can walk in the world, so you can see, for example, the backside of decorative buildings in San Myshuno where you can't actually walk. In this mode, you can also do what I explain previously and hit the "up" key to see the ceiling or up a stairwell to the next floor (and not get the "open to the sky" look you were talking about. You can't play the game in this mode (no way to click on things and interact) you can just have more freedom moving the camera and taking better looking screenshots.

Maybe other people just call it "tab mode"? I've always called it "screenshot mode" because that's what it's good for.