Follow the instructions on box to cook each white cake layer in a 9 inch round pan.
Set cake aside to cool for 10 minutes
Place cakes, once cooled, top sides up in clean 9 inch round pans
Pierce cakes with large fork at ½-inch intervals
Add 1 cup boiling water to each flavor dry gelatin (do separately) and mix each gelatin mixture until the gelatin is completely dissolved
Pour red gelatin over 1 cake and green gelatin over other remaining cake
Refrigerate both cakes for 3 hours
Dip the bottom of "green" gelatin cake pan in warm water for 10 minutes to unmold then dry bottom and flip "green" gelatin cake sized serving plate.
Frost cake with COOL WHIP.
Repeat process with "red" gelatin cake pan
Frost full cake with COOL WHIP
Refrigerate for 1 hour before serving