I've noticed some of the skys were dark on hollidays screenshots... how do you do this?

yeah thats the one im running
ive used that script to do a few things

at night it es_loads cssoundtrack, a nice mod that plays HL music that changes with game play, the more players that are in combat the more intense the music gets

it also loads my est_effects mode at night so the weapon effects come one

you can make the sky dark useing this command

 sv_skyname sky_borealis01