Dissolve each color of Jello in 2 cups boiling water in individual bowls. Stir until Jello is completely dissolved. A 1 cup cold water to each stirring to combine. Refrigerate 1 to 2 hours or until almost set.
Meanwhile, slice strawberries and add sugar. Stir and set aside to develop syrup. Cube angel food cake.
Line a bundt pan with plastic wrap.
Add strawberries (including syrup) to strawberry Jello, and pour into Bundt pan. Mix 2 cups Cool Whip and cubed angel food cake (or, marshmallows if using) into the clear Jello, pour on top of Red Jello. Spread to even. Add Blueberries to Blue Jello, and pour on top of White Jello. Cover with plastic wrap and return to Refrigerator for 3 hours or until ready to serve.
When ready to serve; place serving plate on top of bundt pan and turn over onto counter. Remove plastic, slice and garnish as desired.