Tint buttercream icing pink and blue. To decorate booties on cupcakes, use round tip 12. Beginning at toe end of bootie, pipe a ball with heavy pressure, hold tip at a 45º angle as you move toward back of foot, then bring tip straight up to finish. Indent top of booties with finger dipped in cornstarch. Use round tip 2 to add zigzag cuffs and sting bow to booties.