In large bowl, with mixer on high, beat butter and sugar until light and fluffy, about 3 minutes. Add egg yolks, egg, vanilla, and salt, and beat well to combine.
With mixer on low, gradually beat in flour. Divide dough into 6 equal pieces, roll each piece into an 8-inch log, and chill 15-20 minutes. Working with 1 roll at a time, roll in 1 color of crystal sugar and then wrap in saran wrap. Continue until all are rolled in colored sugar and wrapped.
Refrigerate completed rolls for 3 hours or overnight.
Heat oven to 350°F.
Cut logs into 1/4 inch thick slices, and place on greased baking sheet 1/2 inch apart. Bake 12 to 16 minutes, until golden. Let cool 5 minutes on baking sheet, transfer to wire rack, and let cool completely. Repeat with remaining dough, Makes about 12 dozen cookies.