You make the map not actually dark. Look at these maps for instance,
cp_metalworks
Not actually dark, the skybox and OOB areas may be barely lit, but the ground and places where the players are actually engaging is lit up very well.
de_inferno_cz
While slightly more dimly lit, i think it still holds the same values as metalworks. Strong unnatural lighting along with brighter textures makes the level a lot more fair on gameplay while still keeping the night aesthetic.
de_lite
same scenario