Preheat the oven to 350°F and grease a 9x13-inch cake pan with a nonstick spray and Set aside.
In a large bowl, combine cake mix, water, vegetable oil, and eggs and mix until combined.
Pour the batter into the prepared baking pan and bake for 25 minutes or until a toothpick inserted in the center comes out clean.
Allow the cake to cool for about 30 minutes, then using the handle of a wooden spoon poke holes over each inch of the cake and set aside.
In four small bowls, combine each jello package with 1 cup of boiling water. Whisk together until the jello has dissolved.
Use a tablespoon to pour the jello mixtures into the holes in cake, alternating colors according to preference until each hole has been filled. Do not use all of the jello, about ¼-⅓ cup of each should be used.
Place the cake in the refrigerator and let it chill for 2 hours so the jello sets.
Spread the whipped topping over the cooled cake and top with sprinkles if desired before serving.