Cream the unsalted butter, granulated sugar, and light brown sugar with an electric mixer for 3–4 minutes until light and fluffy.

Add eggs one at a time, beating well after each addition, then incorporate the vanilla extract.

Whisk together flour, baking soda, and salt in a separate bowl, then gradually combine with the butter-sugar mixture.

Fold in semi-sweet chocolate chips until evenly distributed.

Divide dough into 4 portions, color each with gel food coloring, and knead until evenly tinted.

Chill the dough for 15–20 minutes if too soft or sticky.

For marbled cookies, take 1 tablespoon of each color of dough and press together, then roll into a ball.

Preheat oven to 350°F and line baking sheets.

Bake dough balls for 10–12 minutes until edges are golden and centers are slightly underdone.

Let cookies cool for 5 minutes on the baking sheet before transferring to a wire rack.