The trick to achieving the perfect color frosting is to add the coloring liquid, gel, paste or powder a little at a time so the color doesn't get too dark. If you add too much burgundy coloring to frosting, you'll end up with a shade of burgundy that is darker than desired. While you can always mix in more white frosting to lighten the burgundy, this is a waste of sugar and butter or shortening if you don't need the extra frosting. White food coloring, used to remove the yellow tint from buttercream frosting, also works well to lighten dark frosting.
Add a small amount of the white food coloring to the burgundy frosting. The exact amount depends on the type of food coloring and the amount of burgundy frosting you wish to lighten. White food coloring is commonly available in liquid and gel paste forms; it takes much more liquid food coloring than gel paste to change color. To lighten 1 cup of burgundy frosting, for example, start with one drop of liquid white food coloring or just a bit of gel paste on the end of a toothpick. When working with a large mixing bowl of frosting, start with five or six drops of liquid or one drop of gel paste.
Mix the frosting well to fully incorporate the white food coloring, using a wire whisk or electric mixer. Use a rubber spatula to scrape the sides of the bowl and mix some more until you achieve a uniform color with no white or light streaks.
Check the burgundy frosting to see if you're lightened it enough. If you're satisfied with the results after the first addition of food coloring, no further food coloring is required.
Add more white food coloring to the burgundy frosting. If you only want it to be a shade lighter, add the same amount as you added the first time. Add more food coloring at one time if you want to lighten it several shades. Until you get used to mixing frosting colors, it might be best to simply add one small drop at a time. Mix the food coloring thoroughly into the frosting. Repeat this process until you achieve the desired shade.
Add more confectioner's sugar to thicken the frosting if the food coloring thins it out, a common problem associated with liquid food coloring. Confectioner's sugar will further lighten the frosting color, so keep this in mind while adding the food coloring. If the frosting isn't quite light enough, but the liquid has thinned it out, add the sugar to thicken and lighten it to see if additional food coloring is needed.