1Place paper baking cup in each of 15 regular-size muffin cups; spray paper cups with cooking spray. In large microwavable bowl, microwave butter uncovered on High about 45 seconds or until melted.
2Add marshmallows; toss until coated. Microwave uncovered on High about 1 minute 30 seconds, stirring after 45 seconds, until mixture can be stirred smooth. Immediately add cereal and candy corn; stir until evenly coated.
3Firmly press about 1/2 cup cereal mixture into each muffin cup. Cool about 15 minutes or until firm. Remove from pan.
4In small bowl, mix 1 1/2 cups frosting and yellow food color. In another small bowl, mix 1 1/4 cups frosting and orange food color. Leave remaining frosting white. Spoon each color frosting into separate quart-size resealable food-storage plastic bag; seal bags. Cut off 1/2-inch corner of bags; squeeze bags to pipe frosting in layers on cupcakes to look like candy corn. Decorate with candy sprinkles.