In bowl, with electric mixer on low, combine whipped-topping mix and cold milk. Increase speed to high and beat 4 minutes.
In large bowl, whisk together fat-free sweetened condensed milk, lemon juice, and grated lemon peel. Whisk in whipped topping. Blend in yellow food coloring.
Pour mixture into a reduced-fat graham-crumb crust and freeze. Flip the plastic cover from packaging for a lid. Garnish with Cool Whip and fruit slices.
Follow lemon-pie directions, substituting 1/2 cup lime juice, 1/4 teaspoon grated lime peel, and green food coloring for the lemon juice, lemon peel, and yellow food coloring.