Prepare and bake cake mix as directed on package for 24 cupcakes; cool completely. Pierce cupcakes with wooden skewer or large fork at 1/4-inch intervals. Stir boiling water into dry gelatin mix at least 2 min. until completely dissolved. Spoon 2 tsp. of the gelatin over each cupcake. Refrigerate 3 hours.
Tint whipped topping with food coloring; spread about 2 Tbsp. of the whipped topping onto each cupcake.
Cut each large marshmallow crosswise into five pieces with clean kitchen scissors to resemble flower petals. Arrange five of the petals in flower shape on top of each cupcake; place a miniature marshmallow in center of each group of petals. Sprinkle each with 1/2 tsp. colored sugar. Store in refrigerator.