LINE 9-inch square pan with foil. Coat with no-stick cooking spray.
COMBINE 1/3 can sweetened condensed milk (scant 1/2 cup), 2 tablespoons butter and chocolate wafers in microwave-safe bowl. Microwave on HIGH 60 seconds. Stir until smooth and melted. Pour evenly into prepared pan. Chill 20 minutes. Repeat for red and green wafers, adding peppermint extract to the red layer and chilling between layers.
CHILL one hour more. Remove fudge from pan using edges of foil. Remove from foil. Cut into 3/4-inch squares.
*Candy coating wafers can be purchased in larger grocery stores, craft stores or candy supplies stores.