Prep - Preheat oven to 350°F. Spray 9x13-inch pan with baking spray.
Combine - Beat yellow cake mix, water, eggs, and oil in a large bowl with electric mixer on low speed for 30 seconds. Beat on medium speed 2 minutes. Pour sheet cake batter onto pan; spread evenly. Bake 23 to 28 minutes, until toothpick inserted in center comes out clean. Cool completely in pan on wire rack. Stir together frosting and food coloring in small bowl. Mix well until desired pink color is achieved.
Create - If desired, overturn cake onto serving platter, otherwise, use pan as serving platter. Spread frosting evenly over top of yellow birthday cake, then add sprinkles. Slice and serve for a happy birthday!