Hue, which is a glaze, is really great for muting lip color. My lips are berry-shade and Hue mutes them nicely.
I also use MAC's Naked lipliner (LE) with NYX Circe lipstick over top. That gives me a REALLY nude lip and has a glossy finish. I use it in one of my FOTDs (scroll down to see a closeup of the lips)
http://www.specktra.net/forum/thread/171731/fyrinnae-adam-steve-velociraptor-inspired-by-shrinkle
I know it's not MAC, but I don't have a MAC color that makes a nude lip quite like that one. I hope they re-promote Naked lipliner because I would totally buy a backup!