This is from February in case you both missed it and as far as I remember, this issue was sorted on Discord some time ago already. Corrupted video settings (setting some stuff like textures to low automatically even if they were all set to high in game options) were the issue, making game "very dark and muddy looking".
In case someone else will have this problem, to fix it you need to set everything to low, start your game, load a random map, then quit, set your desired settings back and restart the game. It will overwrite corrupted files.