One green, hot, crisp, and pungent. The other red, sweet, slick, and tender. The contrast is essential to the success of antipasto. Both kinds of pepper can be purchased jarred, but roasting the sweet red ones is worth the effort. Char them under the broiler, directly over a gas burner, or over a hot outdoor grill, turning them until black all over. Then drop them into a paper bag, fold it closed, and wait about 15 minutes. The steam inside will loosen the skins; when you come back, you can just slip them off. Pull out and toss the cores and seeds, then slice the peppers into strips. They'll keep for up to 5 days in the refrigerator.