Stir 1 1/4 cups boiling water into each flavor of gelatin in separate bowls until completely dissolved. Pour each flavor into separate 8 or 9" square pans. Refrigerate 3 hours or until firm. Cut each pan into 1" cubes. Arrange rows of different color gelatin cubes to form a rainbow on a large flat tray or cookie sheet. Place 1/2 of the cool whip at each end of the rainbow to form clouds for dipping. Serve immediately or refrigerate until ready to serve.