In a small bowl whisk the egg yolks; set aside.
In medium saucepan whisk together sugar, cornstarch, and salt.
Whisk in coconut milk and lime juice until smooth.
Cook over medium-high heat, stirring constantly, until mixture thickens and comes to a boil.
Remove from heat.
Gradually whisk about 1 cup of the hot pudding mixture into the egg yolks, then whisk the egg yolk mixture back into remaining pudding mixture and return to the heat.
Bring back to a boil and cook for 1 minute, stirring constantly.
Remove from heat and add the butter and optional food coloring, stirring until smooth. Immediately pour filling into the baked coconut crust. Cool at room temperature, then refrigerate until serving time.