OK starting the paint over!
I was using sandy browns and tans. It ended up looking like wood. I went back to reference photos and confirmed that the walls are definitley grey. If you look close, even in the moonlight you can see the sand on the ground and compared to that the walls are grey. Maybe a slight brownish grey. I'm having a tough time creating the right look, so please be patient. This is my first dio and I'm new to airbrushing too. Big learning curve here.