Key Lime Pie

1 8 oz container whipped topping
1 can sweetened condensed milk
1/2 c. fresh lime juice ( can use the frozen concentrate)
small dash of green food coloring (optional)
1 prepared graham cracker pie crust or other

Whisk together whipped topping, condensed milk and lime juice. Spoon into crust. Set in freezer about 30 minutes. Sprinkle lime zest on top.