Beat butter in a mixing bowl with an electric mixer on medium to high speed for 30 seconds. Add granulated sugar and baking soda; beat until combined. Beat in tequila, liqueur, and vanilla. Beat in as much of the flour as you can with the mixer. Stir in remaining flour, walnuts, and lime peel with a wooden spoon. Stir in food coloring to make desired color.
Shape dough into a 6-inch-long log. Roll log in coarse sugar. Wrap in plastic wrap or waxed paper, and chill for 4 hours or until firm.
Cut dough into 1/4-inch-thick slices; cut each slice in half crosswise. Place slices 1 inch apart on an ungreased cookie sheet. Bake in a 350 degree F oven for 8 to 10 minutes or until edges are lightly browned. Transfer cookies to wire racks and cool. Makes about 48.