Preheat oven to 375°

In a large bowl, combine sugar cookie mix, butter, egg, flour and vanilla with a wooden spoon, until a soft dough forms.

Divide dough into 3 (or more) pieces. Place each piece in a seperate bowl.

Add food coloring to each bowl and stir into dough until desired color is achieved.

Place dough in refrigerator for at least 20 minutes. Cold dough is easier to work with.

On a floured surface, or parchment paper, drop balls of each color of dough (I used a 1 TBSP sized cookie scoop) in a random pattern. You want to form a rectangular shape.

Gently push the dough balls together towards the center to tighten up the rectangle.

Roll dough to approximately 1/4 inch thick. This will create the marbled pattern.

Use a cookie cutter to cut shapes out of the dough.

Place cutout shapes 2 inches apart on a baking sheet lined with parchment paper.

Bake for 7-9 minutes, until edges are golden.

Allow cookies to cool on baking sheet for a few minutes before moving to cooling rack to cool completely.

Store in an airtight container at room temperature.