In a large bowl, cream butter and sugar until light and fluffy.
Beat in egg and vanilla.
Combine the flour, salt, and cardamom; gradually add to the creamed mixture and mix well.
Cover and refrigerate for 2 hours or until easy to handle.
Divide the dough and place the favorite colors.
On a lightly floured surface, roll out to 1/4-in. thickness.
Cut with a 2-1/2-in. round cookie cutter dipped in flour.
Place 1 in. apart on ungreased baking sheets.
With the top of a 1/4-cup measuring cup dipped in flour, press an indented edge into each cookie. Using a plastic straw, cut out four holes near the center of the cookie.
Bake at 350° for 10-15 minutes or until edges are lightly browned.