Heat oven to 350º

Place cupcake liners in cupcake pan; set aside.

Mix cake mix, water, oil and eggs in large bowl with mixer on medium speed for 2 minutes.

Divide cake batter into three equal portions. Tint the cake batter two different colors; Sky Blue and Lemon Yellow, leave one portion plain (white), with 4 drops sky blue and 4 drops lemon yellow. Stir until you reach desired color. (Adding more or less gel paste food coloring)

To make marble effect; use a small spoon to alternate small spoonfuls of colored and plain (whitcake batter into cupcake liner. Keep adding and alternating colors until cupcake liner is about 2/3 full. Repeat until all liners are filled.

Bake at 350º for 12-17 minutes. Remove cupcakes from pan, place on a wire rack. Completely cool before frosting.

Prepare frosting:

Divide frosting between two small bowls. Add 4 drops sky blue to one bowl and 4 drops lemon yellow gel paste food coloring to second bowl. Stir until you reach desired color. (Adding more or less gel paste food coloring)

Fit a large pastry bag with a 2D frosting tip, to achieve a swirl effect. Carefully spoon sky blue frosting onto one side of the pastry bag and then carefully spoon lemon yellow onto the other side of pastry bag. Squeeze pastry bag and frost cupcakes. Sprinkle with multi-colored sprinkles.