In a large bowl, cream the shortening and confectioners' sugar until light and fluffy. Beat in egg and extract. Gradually add flour and salt. Tint with food coloring. Cover and refrigerate for 1 hour or until easy to handle.
On a lightly floured surface, roll out dough to 1/4-in. thickness. Cut with a lightly floured 2-in. shamrock cookie cutter. Place 1 in. apart on ungreased baking sheets. Sprinkle with colored sugar if desired.
Bake at 375° for 10-12 minutes or until edges are lightly browned. Cool for 1 minute before removing to wire racks.