Welp, I had the Helis with clear containers upturned over their pots to keep humidity in, but I decided I should put them in a terrarium instead. I left this uncovered today on the balcony, but I get the feeling the humidity isn't enough (and don't want to risk killing a bunch of Helis), so I've put a big clear glass plate on top of it too. This leaves 4 corners (about 2" square triangles of mesh) exposed still for air circulation. They're all sitting in about 1/2" water.
Here's the box sitting in with a bunch of other plants:
I think the best sort of light to bring their color out is sunshine, and I'm sure they love the temp drops outside (at least 10 degrees at night where I live).