Heat oven to 350°F. Spray 13x9-inch pan with cooking spray. In large bowl, beat cake mix, buttermilk, oil, eggs, cocoa and food color with electric mixer on medium speed 2 minutes. Pour into pan. Bake 25 to 30 minutes or until toothpick inserted in center comes out clean. Cool completely. Line cookie sheet with waxed paper. Crumble cake into large bowl. Add frosting; mix well. Shape into 1 1/4-inch balls. Place on cookie sheet. Freeze 15 minutes. Transfer to refrigerator.