Line 12 muffin pan cups with paper liners. Alternately, cheesecakes can be made in 12 mini Mason jars.
In a small bowl, combine graham cracker crumbs and and melted butter. Press one tablespoon of crumbs into the bottom of each liner.
With an electric mixer on medium speed, beat the cream cheese until smooth.
Add the condensed milk and lime juice and mix well. Mix in the food coloring, if using. Fold in the lime zest and 1 cup of the whipped topping.
Divide the mixture evenly among the lined muffin cups. Cover pan with foil or plastic wrap and freeze until firm, at least 3 hours. Let stand about 5 minutes before serving.
Top with remaining whipped topping and fresh lime slices before serving.