In a large mixing bowl, cream butter, shortening and sugars. Add eggs, one at a time, beating well after each addition. Beat in orange juice concentrate and vanilla. Combine the flour, baking soda and salt; gradually add to creamed mixture. Cover and refrigerate for 2 hours or until easy to handle.
On a lightly floured surface, roll out dough to 1/4-in. thickness. Cut with a 3-in. star shaped cookie cutter dipped in flour. Place 1 in. apart on ungreased baking sheets. Bake at 350 degrees F for 7-8 minutes or until edges are firm. Remove to wire racks to cool.
For frosting, combine confectioners' sugar, butter, orange juice concentrate, vanilla and enough milk to achieve spreading consistency. Tint with food coloring if desired. Frost cookies; sprinkle with colored sugar if desired.