It makes colors correct. By default post processing is screwed, so any pixel that should be WHITE or BLACK appears to be GREY. Colors looks dimmed, like if you display very dusted. This mod corrects colors and now they look as they should and as they did in original version of game. Also as little bonus FXAA improved to less blury and more accurate version.

Why would they release the game with incorrect colors? Is there a version of this mod that doesn't change the FXAA?

Hummm Looks like this game is another HD remake in which developers tried to rush things up to get a quick buck from us. Now its up to us gamers to fix what the developers left behind lol. Corporativism at its best

Yep, and the dropped post release support already without finishing things up. Having extra 8 gb of mod sdk installed just to have ability to use tiny mod like this was a temporary solution that stuck forever now, and whole modding process was not really smooth (for example after a while upload tool stopped working and i can upload new version of mod, and damn settings for it aint even allow me to change cover or tag for uploaded mod or reupload it again). Guess why there are not many mods around.