Should you wish to indulge your inner Picasso -- in particular, your perfectionist, wildly demanding inner Picasso -- make your way to Williamsburg Art Supply (125 East 4th Street; 529-9585). For almost nine years, this small shop has been outfitting art luminaries like Brice Marden and Louise Fishman with an extravagant array of paints available nowhere else -- the base pigments are procured and hand-ground exclusively by WAS, and no more than five gallons are produced at a time. Fishman has been a fan of WAS since its birth. "It's the easiest place in the world for me to shop," she remarks. "There's no fluff there," she adds, "it's really for the working artist." Admittedly, with only about 700 square feet, this isn't Pearl Paint (though you can find rarer stuff here, like handmade Escoda brushes from Barcelona), but Marden praises the "simple, functional" shop by recognizing its purity of purpose. "They don't stock things with shelf life in mind," he notes, "but with painting in mind."