Prepare lime, orange, and cherry flavored gelatins separately, according to package directions, using 1 cup boiling water and 1/2 cup cold water for each. Pour each into a separate 8x8-inch pan. Refrigerate until firm.
In medium bowl, combine lemon gelatin, sugar and remaining 1 cup boiling water. Stir until gelatin and sugar are dissolved. Stir in pineapple juice and chill in refrigerator until slightly thickened.
Cut firm gelatin into 1/2-inch cubes. Prepare whipped topping according to package directions. In a large bowl, combine whipped topping with lemon gelatin-pineapple juice mixture. Fold in cubed gelatin and pour into mold. Chill 5 hours or overnight before serving.
