We're producing all the artwork for ours in a greyscale (0%, 33%, 66% and 100%) palette that gets swapped out by a shader in-engine for our actual palette.
Haven't decided on the actual palette yet but it'll likely default to the olive green and then offer a couple of different options users can switch between.
Kinda like what I've done here for the title screen of another game. Just for funsies, kinda like whacking the game into a Super Gameboy style device or a GC Gameboy Player where you can choose palettes to overlay onto the original.