Just a small edit of existing .lua file to darken the Normandy 2.0 map. Made for JSGME or similar mod managers, put the "Darker_Normandy" folder in your _MODS folder to install.
To tweak the mod further, go to ShadingOptions.lua in "Darker_Normandy\Mods\terrains\Normandy" and change the first three gamma values. Lowering the numbers will make the map darker.
The vanilla game values are:
surface 0.92000000572205
objects 0.85299998283386
trees 0.94000000000000
Forum link:
https://forum.dcs.world/topic/324445-darker-normandy-mod/#comment-5203220