If I leave the game in windowed or borderless mode, the colors are washed out. If I put it in full screen, the colors are brighter but everything that's bright is blindingly bright. Like can't see anything around it. Muzzle flash, daylight, everything is a flashbang. I can't even see the main menu labels because they generate so much peripheral light. What's the deal?

Probably something related to HDR, try to calibrate it in the game settings alongside the brightness and gamma blah blah blah, or totally disable HDR.