I don't do dark color schemes very often, and I paint heavily weathered dark color schemes even less! This is one of those rare times, and it is for the Hexenheim Stormtroopers made by Victoria Miniatures.
Here's a link to the store where you can see how the various parts work together:
It can be challenging enough to keep a "compressed" color scheme interesting, but when it is this dark you have to find those variations wherever possible. That might mean putting a touch of dark green in the shadows of something which seems reddish, or putting some blueish tints in coats that are supposed to be a warm gray.
That can be even more important when you are going to add weathering effects like mud spatter.
On these figures, the mud spatter had to be a warm tan color, so the coats had to be a 'neutral' tone. Ideally that would be slightly cooler, because the warm mud tones would contrast with that a little more.
Of course, having very bright and saturated elements like the glowing eye pieces and the targeting lights help to make a good place for the eye to focus on.
Normally I work in much brighter and saturated color ranges. However, it is possible to get far more color into a so called limited palette.
Here's a link to the Broolian Beastmen video, which also involved a "compressed" color range:
