PLACE cakes, top-sides up, in clean 9-inch round pans; pierce with large fork at 1/2-inch intervals.
ADD 1 cup boiling water to each flavor dry gelatin mix in separate small bowls; stir 2 min. until completely dissolved. Pour red gelatin over 1 cake and lime gelatin over remaining cake. Refrigerate 3 hours.
DIP bottoms of cake pans in warm water 10 sec.; unmold. Fill and frost cake layers with COOL WHIP. Refrigerate 1 hour. Top with raspberries if desired.