Mile-High Lime Pie

1 can (14 ounces) sweetened condensed milk
1 cup (8 ounces) sour cream
1/3 cup plus 2 tablespoons lime juice
5 drops green food coloring, optional
1 carton (8 ounces) frozen whipped topping, thawed
1 graham cracker crust (8 inches)

In a bowl, combine the milk, sour cream, lime juice and food coloring if desired. Fold in whipped topping. Pour into the crust. Refrigerate for at least 12 hours. Makes 8 servings.