I think that you could just have all the colors be drab, no "screen" needed. Also, you could play up the lights as well, for example, according to the Grimmerie, Elphaba always has a green light on her to accentuate her makeup. Also, I think that the citizens could have very boring, monotonous 3 note songs, almost like a chant. I could see the Giver and Jonas having some wonderful songs together, changing the storyline a little to have Jonas hear music before he arrives to Elsewhere. I could also see Jonas' little sister, Lily, having solo.....
Just my thoughts.
Hunter: Your teeth need whitening./ Heidi: You sound weird./ Jeff: You taste funny.
-Jeff Bowen's worst onstage line flub.