Place cake layers top side up in two 9-inch round cake pans. Pierce cake layers with a large fork at 1/2 inch increments. Stir 1 cup boiling water into each flavor of the gelatin in separate bowls for 2 minutes or until dissolved. Carefully pour 1 gelatin over 1 cake layer and the other gelatin over the second cake layer. Refrigerate for 3 hours. Dip 1 pan in warm water for 10 seconds; unmold onto a serving plate. Spread with 1 cup of whipped topping. Unmold the second layer and carefully place it on top of the first layer. Frost with remaining whipped topping. Garnish as desired. Refrigerate for 1 hour before serving.