1 can sweetened condensed milk
3/4 c. lime juice (bottled is okay, but fresh is better)
Finely grated rind of 1 lime
1 to 2 drops green food coloring, optional
1 (8 oz.) tub whipped topping
1 lg. store-bought graham cracker crust
Lime slices, optional

In a large bowl, mix sweetened condensed milk with lime juice. Stir in grated rind, food coloring. Fold in whipped topping. Pour into graham cracker crust and chill for several hours, preferably overnight. Top with lime slices.