Preheat oven to 400F.

In a large mixing bowl, whisk sugar into softened butter until creamy and fluffy.

Ensure the mixture is light in color.

Slowly stir in eggs, one at a time, making sure each egg is thoroughly incorporated.

Mix in vanilla extract.

Stir in milk, 1 tablespoon at a time, stirring thoroughly after each addition.

Divide the batter evenly into 6 smaller bowls.

Add food coloring to each bowl according to the following:

Bowl #1: 8 drops of red food coloring.

Bowl #2: 8 drops of yellow and 4 drops of red food coloring (for orange).

Bowl #3: 8 drops of yellow food coloring.

Bowl #4: 8 drops of green food coloring.

Bowl #5: 8 drops of blue food coloring.

Bowl #6: 8 drops of blue and 4 drops of red food coloring (for purple).

Mix each bowl well until the color is evenly distributed.

Line a muffin pan with muffin cups.

Starting with the purple batter, spoon a layer evenly into each of the muffin cups.

Spread the batter slightly, continue layering the colors in the following order: blue, green, yellow, orange, and red.

Bake for approximately 20 minutes at 400F, or until a toothpick inserted into the center comes out clean.

Let the cupcakes cool completely.

Top with your favorite frosting (white frosting is recommended to highlight the colors).

Enjoy!