Heat oven to 200°F. Grease 2 large cookie sheets with shortening or cooking spray. In small bowl, beat egg whites, cream of tartar and salt with electric mixer on medium speed until foamy. On high speed, add sugar, 1 tablespoon at a time, beating until sugar is dissolved, meringue is glossy and very stiff peaks form. Beat in mint extract. With rubber spatula, fold in food color, 1 drop at a time, until well blended and desired color.