Dissolve each flavor of jello completely in 2 cups of boing water inseparate bowls. Stir 1 cup of cold water into each bowl. Pour into separate9x13 inch pans. Refrigerate at least 3 hours until firm.
Cut into 1 cm cubes. Place blue jello cubes in bottom of clear glass trifle bowl. Top with one third of the Cool Whip. Add cake cubes, then sliced strawberries. Top with another one third Cool Whip. Add the red jello cubes and then the remaining Cool Whip. Sprinkle blueberries over top if desired.
Refrigerate before serving.