Preheat your oven to 350°F and grease a 9x13-inch baking dish.

In a mixing bowl, combine the cake mix, eggs, vegetable oil, and water per package instructions and mix until smooth.

Divide the batter into 3-4 bowls. Add gel food coloring to each for pastel hues and fold gently.

Spoon blobs of colored batter into the baking dish, alternating colors.

Gently swirl the different colors of batter with a butter knife for a marbled effect.

Bake for 28-32 minutes until a toothpick comes out clean. Let cool for 15-20 minutes.

Poke holes all over the cake's surface using a wooden spoon handle.

Whisk the pudding mix with milk until thickened, then pour it over the cooled cake, ensuring it fills the holes.

Cover with plastic wrap and refrigerate for at least 2 hours, preferably overnight.

Spread Cool Whip on top of the cake once chilled. Decorate as desired.