In large bowl, mix powdered sugar, meringue powder, vanilla and 1/2 cup of the warm water. Beat with electric mixer on medium speed about 1 minute or until frosting becomes a thick spoonable glaze. If frosting is too thick, stir in additional warm water, a small amount at a time. Stir in food color, adding more if needed to achieve desired color. Spoon warm frosting over each cookie, coating completely and allowing excess frosting to drip off. Let stand 20 minutes to set.