Preheat oven to 350º.

In a large bowl combine graham cracker crumbs and sugar. Add butter and toss until combined. Press into the bottom of a 9 x 13 baking pan coated with cooking spray.

Bake until firm, approximately 10 minutes. Cool on a wire rack for approximately 20 minutes.

In a small bowl, combine sweetened condensed milk and lime zest. Set aside.

When crust is cooled, top with macadamia nuts, white chocolate chips and M&Ms. Pour condensed milk over the top, spreading to cover completely. Sprinkle coconut evenly on top of condensed milk.

Bake until coconut is toasted, 10 to 15 minutes. Transfer to rack to cool completely before cutting.