Place semi-sweet chocolate and 6 ounces of the white chocolate in large microwavable bowl. Add sweetened condensed milk; mix well. Microwave on HIGH 2 to 3 minutes or until chocolate is almost melted, stirring after every minute. Stir until chocolate is completely melted. Stir in food color and vanilla.
Pour chocolate mixture into foil-lined 9-inch square baking pan. Sprinkle with remaining 2 ounces chopped white chocolate.
Refrigerate 2 hours or until fudge is set. Use foil to lift out of pan onto cutting board. Cut into 36 pieces. Store in tightly covered container at cool room temperature.