Welp, this project is going faster than I expected. After trying one or two color combos I just opted to go super easy, with a simple dry brushed layer of Bleached Bone over Testors Light Earth flat spray paint.
To break up the monotony, I've added a few little tufts here and there in a variety of colors representing alien shrooms, fungi, or flowers that apparently don't need any light. Several columns and wall sides are also 'ard coated to look wet but that doesn't show up in these pics.
The two cave entrances that I have painted thus far are flocked mainly on the outside and around the arch undersides, representing the forest beyond.
These are fairly quick and easy to do, and am batch painting them at a rate of a half dozen at a time. Already about a third of the way done, I'm hoping I can push thru the rest before running out of steam, with my hobby butterfly wandering off to paint something else.