In large bowl, beat cake mix, water, oil, egg whites and peppermint extract with electric mixer on low speed 30 seconds. Beat on medium speed 2 minutes, scraping bowl occasionally. Divide batter in half. To 1 portion, add food color; stir until uniform in color. In each muffin cup, place 2 tablespoons red batter; top with 2 tablespoons white batter. Swirl white batter through red batter with knife for marbled design.