1. 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.
2. Refrigerate dough about 2 hours or until firm.
3. 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.
4. Bake 6 to 8 minutes or until lightly browned. Cool on baking sheets 1 minute. Remove to wire racks; cool completely.
Colored Sugar: Place 1/2 cup granulated or sanding sugar in resealable plastic bag. Add 5 drops of McCormick® Assorted Food Colors and Egg Dye or McCormick® Assorted NEON! Food Colors and Egg Dye. Add more food color, a drop or two at a time, if more intense color is desired. Seal bag and knead gently to disburse color throughout the sugar. Spread in a thin layer on a baking sheet and break up any large lumps. Allow to dry thoroughly, about 15 to 20 minutes. Sift or press through sieve to return sugar to its original texture, if needed.
Flavor Variations: Prepare as directed. Use McCormick® Pure Almond Extract or Pure Lemon Extract in place of the vanilla.