Preheat oven to 325°F In medium mixing bowl, beat egg yolks; gradually beat Eagle Brand and lime juice. Stir in food coloring, if using. Pour into pastry shell.
Bake 30 minutes. Remove from oven. Increase oven temperature to 350°F.
Meanwhile, for meringue, with clean mixer, beat egg whites and cream of tartar to soft peaks. Gradually beat in sugar, 1 tablespoons 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. Chill at least 3 hours. Store covered in refrigerator.