Preheat the oven according to the cake mix directions. Line a cupcake pan with liners.
Prepare the cake mix according to the package directions.
Divide the batter evenly into three separate bowls. Color one bowl of batter red and one bowl blue with the gel food coloring, leaving the third bowl white.
Spoon about 1 tablespoon of blue batter into each liner. Spoon about 1 tablespoon of white batter on top of the blue in each liner. Spoon about 1 tablespoon of red batter on top of the white in each liner.
Bake until a toothpick inserted in the center comes out clean. Cool the cupcakes completely.
Spoon the frosting into a piping bag, or spread it on with a spatula. Decorate the frosted cupcakes with red and blue sprinkles.
Notes
Layer in the Right Order: Always spoon the batter in as blue, then white, then red, so the colors stay distinct once baked.
Check Doneness with a Toothpick: A clean toothpick means they're done; overbaking dries the cupcakes out quickly.
Cool Completely Before Frosting: Warm cupcakes will melt the frosting right off the top.
Use Room Temperature Eggs: Room temperature eggs blend into the batter more evenly than cold ones.
Storage Tip: Store frosted cupcakes in an airtight container so they don't dry out before serving.