This feels like the broad brush strokes of an incredibly memorable play session. The party enters a dreamlike place, called by a mysterious horn and traveling through a tunnel that dumps them in another realm (kind of like C.L. Moore's Black God's Kiss). Return is difficult, but possible. The sensory possibilities here could make for something really unique.
But the town feels like it needs a little more to engage with and see. Otherwise, I'm afraid a party will knock out a guard, grab the horn and orb, and head home without really connecting with the surreality of the Sunset Empire.
If they turn green, what happens? Is a member of the party originally from here and got called home? Do they resemble any villagers, missing children, or are they a descendant of the "wanton and impudent" girl? Is there more to explore if my players decide to stay? Maybe these are all Warden questions, but I want to learn a little more about the Sunset Empire.