Multi-colored cakes can be fun for a lot of reasons. They can help you show team spirit on an important game day, turn plain cupcakes into a great theme dessert or simply hint at the flavor inside a baked good. It is easy to add food coloring into cake batter, but there are some challenges to ensuring your cake comes out the way you envision it.
How much color do you need? Recipes often only hint at the amount of food coloring needed because the amount you might need will vary widely depending on the coloring you use. High quality gel and paste food colorings require a smaller amount of coloring than liquid colorings to get your desired color, but they can require extra mixing to break up the gel and mix it in completely. Food coloring is not an exact science and you will need to add more color as you go if you think that you’re not going to get the color you want. I recommend bring generous with your coloring unless you are aiming for a pastel cake, because vibrant colors usually make the biggest impact. The color is never going to look brighter after baking, so if it doesn’t look bright enough in your mixing bowl, you probably need more.
What if I use too much? Many people worry that adding food coloring will change the consistency of their batter. Neither liquid nor gel food colorings will add enough liquid to alter the consistency of a standard cake batter and prevent it from baking properly. It would have to be a very extreme amount of food coloring to change a batter that much (at least a bottle of coloring for one standard recipe), and you should never need that much coloring to dye one standard recipe.
What kind of food coloring should I use? Gel and paste food colorings deliver more intense color than regular liquid food coloring and are available in a much wider array of colors. You may have to make a trip to a store that is very well stocked with cake supplies (or shop online) to pick up the colors you want, however, since most regular grocery stores don’t carry a wide variety of colorings. They’re the best choice if you are set on getting your batter to a very particular or very vibrant color.
When should I add in the food coloring? As you add in more and more coloring, you need to mix it in to the batter. With a cake mix (vs homemade cake), you can get away with a lot of stirring, but eventually all cake batter will toughen up with lots of mixing and you will end up with tunneling in your cake instead of a nice even, tender crumb. I prefer to add my food coloring as I am combining the liquid and dry ingredients of a recipe, before the batter is completely combined. This way, I still have time to add more as I go without overmixing my batter. That said, if you feel you batter has been mixed very vigorously, you can let it rest for a few minutes before putting it into the oven and that will help the gluten to relax slightly before baking.