1. Add melted butter to graham cracker crumbs and mix until combined.
2. Press crumb mixture evenly into the bottom and up the sides of a 9 inch pie pan, then set aside.
3. Combine cream cheese and sugar and mix until smooth.
4. Add lime juice, tequila, orange liqueur and lime zest and mix until completely combined.
5. Fold in the Cool Whip and green food color, if desired.
5. Spread filling evenly into crust and refrigerate for several hours, until firm.
6. When ready to serve, top with additional Cool Whip and lime zest.