Mix sugar, cornstarch, half-and-half, and salt in saucepan. Cook to boiling point. Add vanilla, food coloring, if using, and the butter; return to heat.
Cook, stirring constantly until thickened. If there are any lumps, put through a fine sieve. Pour the mixture into pie shell and sprinkle with nutmeg.
Bake at 325° for 35 to 45 minutes or until firm and lightly browned.
Serves 6 to 8.