Fly casual, and wear something you don't mind getting snagged on ancient stadium seats or a tree branch. Berkeley has nice warm football weather year-round. But whatever you do, don't wear anything red, lest the aforementioned organizational powers of the student section focus on destroying you. Cal has what one of our Bear correspondents calls "A great history of attacking opposing team mascots," so you don't want to be rocking anything that could possibly identify you with, say, the Stanford Tree. (Pieces of its 1996 costume are still on display in fraternities.)