In a small bowl, whisk together flour and salt. In medium size bowl, beat butter until creamy, about 1 minute. Beat in sugar until fluffy, 2 minutes or so. Beat in yolks and vanilla. Stir in flour mixture until dough comes together. Divide dough into quarters.

Roll each quarter of dough into a 6-inch log that is 1-inch thick. On a cutting board spread the decorator's sugar in a rectangle, about 7 x 5 inches. Roll 2 of the logs in colored sugar to evenly coat edge. Wrap each log in plastic wrap and refrigerate. Refrigerate 2 hours or overnight.

Heat oven to 350 degrees F. Unwrap logs. Cut each log into 16 slices about 1/4 inch thick. (Depending on your logs, you may get more or less.). Transfer slices to ungreased baking sheets.

Bake cookies at 350 degrees F for 12 to 14 minutes or until just golden around the edges. Darker baking sheets will darken cookies more quickly than lighter ones, so keep an eye on them. Remove from cookie sheets to wire rack to cool completely. Store in airtight container for up to 2 weeks.