In large bowl, mix icing sugar and butter with spoon or electric mixer on low speed. Stir in vanilla and 3 tablespoons of the milk. Gradually beat in just enough remaining milk to make frosting smooth and spreadable. If frosting is too thick, beat in more milk, a few drops at a time. If frosting becomes too thin, beat in a small amount of powdered sugar. Tint frosting with orange paste food colour. Place 1/2 cup frosting in small resealable food-storage plastic bag; seal bag and set aside. Frost cupcakes with remaining orange frosting.