There is a whole genre of series that I dare to call "grey shows", where they seem to have forgotten the concept of a colour palette.
Witch Hunter Robin,
Wolf's Rain,
Gilgamesh,
Texhnolyze etc all belong in this category.
Ergo Proxy is simply the latest (and one of the murkiest) additions. So dark, sometimes, you can't even see what is going on, unless you have a super hi-res version, which I don't.
My synopsis for the AVCon brochure, pointing this out, was meant to be taking the piss, and I didn't expect them to actually use it. They were either running out of time for printing it out or someone thought it worth keeping.