In a bowl, cream butter and sugar. Blend in egg yolks. Add flour, 1 cup at a time, beating well after each addition. Dough will be very stiff.

On a well-floured surface or pastry cloth, roll out dough to a 1/8 in. thickness. Using a pastry wheel or knife, cut into 2 1/2 in. squares, diamonds, or rectangles. Place 1/2 in. apart on ungreased baking sheets. Sprinkle with colored sugars.

Bake at 375* for 7-8 minutes or until lightly browned.