Our HT has a brown color scheme, primarily because we didn't want to replace the newer carpet (it's a newer home) so we designed the room to match. We used two colors: one for the side walls (incl. front&back) and one for the angled and flat ceiling. For the side walls we went with a flat, dark brown. Looks black when lights are out. For the ceiling, we went with a color called "Colonial Grey" which is a more muted, drab, cup of coffee, brown.
When it was first going up, we weren't too sure. Now, as we are putting on the finishing touches (which takes forever), it was the perfect choice. We want our room to also serve as a fancier guestroom/sitting room when it's not movie time and these rich/dark/brown colors serve that well.