If you've ever tried to make red frosting using store-bought red food coloring, you've probably had less than stellar results. It typically turns out pink or orange, or if you've used too much food coloring, the icing is almost black and has a very bitter taste. It is best to use gel or paste food colorings that offer a much more vivid coloring than the liquid drops from the store. Prepare your icing the day before to allow the color to darken to your desired shade.
Place the frosting into a mixing bowl.
Add about 1/2 tsp. of a red gel or paste food coloring for every one cup of frosting you have. Blend until you have a red color that is just a shade lighter than the shade you want the red to be.
Cover the bowl tightly with plastic wrap and place it in the refrigerator. Leave the icing overnight in the refrigerator. The red icing will darken overnight so that the next day the color will be the shade you wanted.