Right now in the README, you can see minimum system requirements for "Low" and "High" quality. Under High quality, one of the features listed is: "Realtime Lights and Shadows". I think that the hardware mentioned in "High" is good for dynamic lights and shadows, but not realtime world lights and shadows, which bring the framerate down by a lot. I think there should be three sections: Low, Medium, and High.

Low should be what "Low" is now.
Medium should be what "High" is now.
High should include what system requirements are needed to run Nexuiz with all effects on at a reasonable framerate. \

Texture quality and color depth should be mentioned somewhere in the requirements.

Also, the recommended video cards list (http://www.alientrap.org/forum/viewtopic.php?t=349) should be added to the README somewhere.

I would rather call them what they are called now, and add "insane", "noone should nned this" or similar for your "high"

Hehe, actually i think the requirements are quite ok.. but yeah mentioning the cards is a good idea.