Preheat the oven to 350°F (175°C) and grease a 9x13-inch baking dish.

In a large bowl, prepare the white cake mix according to the package instructions, mixing in eggs, water, and oil until combined. Divide the batter into four equal portions, adding different gel food coloring to each.

Spoon dollops of each colored batter into the greased baking dish, alternating colors and swirling gently to create a marbled effect. Bake for 25-30 minutes or until a toothpick inserted into the center comes out clean.

Let the cake cool for about 10 minutes, then poke holes evenly throughout the cake using a wooden spoon handle. Allow to cool completely.

Whisk together the instant pudding mix and milk for about 2 minutes until thickened. Pour the pudding over the cooled cake, making sure it seeps into the holes. Refrigerate for at least 2 hours.

Whip the heavy cream and powdered sugar until soft peaks form. Spread the whipped topping over the pudding layer and garnish with colorful candies or sprinkles before serving.