In a large bowl, combine white cake mix, 3 egg whites, 1 1/3 cups buttermilk, and 2 tablespoons vegetable oil. Mix with an electric mixer for 2 minutes on high speed. In a separate bowl, combine yellow cake mix, 1/2 cup buttermilk, 1 egg, cocoa, red food coloring, and vinegar. Use an electric mixer to beat for 2 minutes on high speed.