STIR 1 cup of the boiling water into each flavor gelatin in separate bowls at least 2 minutes until completely dissolved. Stir 1 cup cold water into each bowl. Pour into separate 8- or 9-inch square pans.
REFRIGERATE 4 hours or until firm. Cut gelatin in each pan into 1/2-inch cubes.
LAYER alternating gelatin flavors and 1-1/2 cups of the whipped topping in 8 dessert glasses. Garnish with remaining 1/2 cup whipped topping.