Preheat oven to 325 degrees F.
In medium bowl, beat egg yolks, gradually beat in condensed milk, lime juice, and food coloring until smooth. Pour into pie crust. Bake 30 minutes.
Remove from oven. Increase oven temperature to 350 degrees F.
Meanwhile, for a meringue (optional) beat egg whites and cream of tartar to soft peaks. Gradually beat in sugar, 1 tablespoon at a time. Beat 4 minutes or until stiff, glossy peaks form and sugar is dissolved.
Immediately spread meringue over hot pie, carefully sealing to edge of crust to prevent meringue from shrinking. Bake 15 minutes.
Cool 1 hour and chill at least three hours. Store covered in refrigerator.
NOTE: This pie can be just as delicious if garnished with twisted lime slices and dolloped with heavy whipping cream, instead of the meringue.