The best stuff I've found is (amazingly) the stuff Uncle Sam hands out, the Army 2-piece tan flightsuit or ADCU. Lightweight as hell, obviously light in color, and bowel-movement friendly! Should see more of em on the market as the new digital pattern stuff comes out.
http://cgi.ebay.com/US-ARMY-DESERT-F...QQcmdZViewItem
I'm hanging on to mine for as long as I can.
-Mike