Rainbow Doughnut Icing

In large bowl, mix powdered sugar, milk and corn syrup until smooth. Divide icing evenly among 6 small bowls. Add a different color gel to each bowl; stir to blend. Place each color icing in small resealable food-storage plastic bag. Cut off tiny corner of each bag.

Place cooling rack on large cookie sheet; place doughnuts on rack. To make a rainbow on each doughnut, pipe one stripe of red, orange, yellow, green, blue and purple icing over top and slightly over edge of doughnut so that colors just touch. Pipe 1 or 2 doughnuts at a time so icing can blend together slightly before setting. The icing will spread slightly and drip down sides. Let stand at least 30 minutes or until icing is set. Store in tightly covered container.