Preheat oven at 350. Prepare 2-9" round cake pans with cooking spray and flour. Prepare, bake, and cool cake mix as directed on package for 2-9" round cake layers. Place cake layers, top sides up, in prepared cake pans. Pierce cake with large fork at 1/2" intervals. Stir 1 cup of the boiling water into each flavor of gelatin in separate bowls 2 minutes or until dissolved. Carefully pour red gelatin over 1 cake layer and lime gelatin over second cake layer. Refrigerate 3 hours. Dip 1 cake pan in warm water 10 seconds; unmold onto serving plate. Spread with about 1/4 of the frosting. Unmold second cake layer; carefully place on first layer. Frost top and sides of cake with remaining frosting. Refrigerate 1 hour or until ready to serve.