In a small bowl, add 3/4 cup boiling water to 1 gelatin package; stir 2 minutes to completely dissolve. Stir in 3/4 cup cold water. Pour into a 3-qt. trifle or glass bowl. Refrigerate until set but not firm, about 40 minutes., In a clean bowl, dissolve another gelatin package into 1/2 cup boiling water. Stir in 1/2 cup cold water and 1/2 cup milk. Spoon over the first layer. Refrigerate until set but not firm., Repeat 5 times, alternating plain and creamy gelatin layers. Refrigerate each layer until set but not firm before adding the next layer. Refrigerate, covered, overnight. Serve with whipped topping and, if desired, fruit.