Mix flour, cream of tartar, baking soda and salt in large bowl. Set aside. Beat sugar and butter in large bowl with electric mixer on medium speed until light and fluffy. Add eggs and vanilla; mix well. Gradually beat in flour mixture on low speed until well mixed.
Refrigerate dough 2 hours or until firm.
Preheat oven to 400°F. Shape dough into 1-inch balls. Roll in additional sugar or Colored Sugar. Place 2 inches apart on baking sheets.
Bake 6 to 8 minutes or until lightly browned. Cool on baking sheets 1 minute. Remove to wire racks; cool completely.