1Heat oven to 350°F. Spray 24 regular-size muffin cups with cooking spray. In medium bowl, mix brownie mix, oil, water and eggs. Divide batter among muffin cups. Bake 13 to 18 minutes or until centers are set and toothpick inserted near edge of cupcake comes out clean. Cool 30 minutes. Run metal spatula around edge of each brownie; lift out to remove from muffin cup.
2In microwavable bowl, microwave vanilla chips uncovered on Medium (50%) 30 to 45 seconds, stirring every 15 seconds, until melted. Cool slightly.
3In medium bowl, beat powdered sugar, butter, milk and food colors on medium speed until fluffy. Stir in melted vanilla chips. Spoon frosting over cooled cupcakes; top each with candy bar.