PREPARE cake batter and bake in two 9-inch round layer pans as directed on package. Cool in pans 15 min. (Do not remove cake layers from pans.)
STIR boiling water into dry gelatin mixes at least 2 min. until completely dissolved. Pierce cakes with large fork or skewer at 1/2-inch intervals. Pour half the gelatin over each cake layer in pan. Refrigerate 4 hours or overnight.
UNMOLD one of the cake layers onto serving plate; spread with 1/2 cup of the whipped topping. Unmold second cake layer; carefully place on top of cake layer on plate. Frost top and side of cake with 2 cups of the remaining whipped topping. Tint remaining whipped topping with food coloring; spread on top of cake to resemble ice rink. Outline outside edge of "ice rink" with decorating gel. Refrigerate at least 1 hour.
DECORATE top of cake with candies. Add graham snacks for the "ice skaters." Decorate ice cream cones with green decorating icing; place around ice rink. Sprinkle cake with the coconut and powdered sugar. Serve immediately or refrigerate up to 2 hours before serving. Store leftover cake in refrigerator.