Combine 1 packet unflavored gelatin with each package of flavored gelatin; add 1 cup boiling water to each, stirring until dissolved. For each, add enough ice to 1/2 cup water to equal 1 cup. Add into gelatin mixture, stirring until slightly thickened; remove unmelted ice cubes. Refrigerate 15-20 minutes.
Spray mold with vegetable pan spray. Stir half a container whipped topping into each gelatin mixture. To deepen color, mix in orange or yellow icing colors. Pour mixture into molds. Refrigerate to set, about 4 hours.
Carefully unmold. Using tinted whipped topping in cut parchment bag, pipe pumpkin stem. Using tip 2, pipe veins on leaves.