HEAT oven to 350°F.
PREPARE cake batter and bake as directed on package for 24 cupcakes.
IMMEDIATELY remove cupcakes from pans to wire rack. Cut each cupcake horizontally in half. Top bottom half of cupcake with 5 marshmallows; cover with top of cupcake. Cool completely.
MEANWHILE, microwave 1 cup marshmallows and milk in large microwaveable bowl 2 min. or until marshmallows are completely melted and mixture is well blended, stirring every 30 sec. Cool slightly. Stir in COOL WHIP and food coloring until blended.
SPREAD cupcakes with COOL WHIP mixture. Top each cupcake with 3 candy corn.