Spray a bundt pan well with cooking spray. Prepare cake mix according to box directions.
Pour one third to one half of batter into bundt pan. Reserve 1 tablespoon JELL-O mix for frosting and add remaining mix to remaining cake batter. Stir just till well blended. Spoon batter into bundt pan over top of your white batter. Do not fill bundt pan past 2/3 full. Place any remaining batter in paper lined muffin tin for cupcakes. Bake cake for 45-55 minutes in a preheated 350 degree oven. (cupcakes for 19-22 minutes) Test for doneness using a toothpick. Remove from oven and let cake cool in pan for 20 minutes before inverting onto plate to cool completely.
You don't need the whole can of frosting for the cake so ice cup cakes first then place remaining frosting in a small saucepan. Heat on low, stirring occasionally just until frosting starts to turn melt, about 3-4 minutes.
You're looking for a smooth flow off the spoon. Place half of the melted frosting in a plastic bag. Add the reserved 1 tablespoon JELL-O mix to the remaining frosting, stir well. Place your JELL-O frosting in a separate plastic bag. With scissors, cut one corner off of each bag. You want the hole as small as possible. Drizzle melted frosting over cake, alternating colors.