In 2-quart saucepan, mix 1 1/2 cups granulated sugar, the cornstarch and salt with wire whisk. Beat in cold water and lemon juice. Add egg yolks; beat until smooth. Add butter; gradually stir in boiling water. Heat to boiling over medium heat, stirring constantly. Boil 2 minutes. Remove from heat; add lemon extract, lemon peel and food colour. Cover surface with plastic wrap. Cool 30 minutes. Pour into pie plate. Refrigerate 30 minutes.