''The tone of Vol. 2 was more of a spaghetti Western, so we wanted a rugged, earthy look,'' says Kill Bill costumer Cat Thomas. Hence the Bride's (Uma Thurman) mustard yellow jacket and phoenix-emblazoned cowboy boots. The leather jacket was ''perfect desert camouflage,'' and the phoenix symbolized ''rising from the dead,'' says Thomas, who designed both items. But the most important rule for dressing a Viper? ''If a woman knows she's going to kick ass, she's not going to wear a miniskirt.''