In a large bowl, cream butter, sugar and salt until light and fluffy. Beat in egg yolk and vanilla; gradually beat in flour. Divide dough in half; mix food coloring into 1 half. Roll each dough portion into a 6-in. square. Wrap each in plastic; refrigerate at least 1 hour or overnight., Preheat oven to 350°. Cut each dough into 36 squares. Working with a quarter of the dough at a time, keep remaining dough refrigerated. Roll 1 piece of plain dough into a 6-in. rope; roll 1 piece of red dough into a 6-in. rope. Place ropes side by side. Lift left rope over the right; repeat to form a twist. Repeat with remaining dough. Curving top of each twist to form hook of cane, place 1 in. apart on parchment-lined baking sheets., Bake 7-9 minutes or until set. Cool on pans 3 minutes. Remove to wire racks to cool.