I am also having my reception at a historic theater (it looks much like the one you are using!)
I am planning on having our color scheme be deep purple, ivory, and bright green, with a hint of gold. I'm trying best to compliment the very regal inside of the theater while still having a bit of summer incorporated into the whole thing.
I think that you should go with gold napkins. I think that it is important to incorporate a touch of gold into your color scheme to really tie in the feel of the theater.
Good luck!