Preheat your oven to 350°F (175°C) and grease a 9×13-inch baking pan.

Prepare the white cake mix according to the package instructions and divide the batter into four bowls. Add pastel colors to each bowl.

Spoon alternating dollops of each colored batter into the prepared pan. Evenly fill the pan without mixing colors.

Bake the cake according to package instructions, usually around 25–30 minutes, until a toothpick comes out clean.

After cooling for 10 minutes, poke holes in the cake with a wooden spoon handle, about 1 inch apart.

In a separate bowl, whisk together the pudding mix and milk until smooth. Pour the pudding over the warm cake.

Cover the cake with plastic wrap and refrigerate for at least 4 hours or overnight to allow the pudding to set.

Whip the heavy cream with powdered sugar and vanilla extract until stiff peaks form.

Spread the whipped topping over the set pudding layer and decorate with festive sprinkles before serving.