In a medium mixing bowl, whisk together vegetable oil and granulated sugar until smooth. Add eggs and vanilla extract, mixing until incorporated.

In a separate bowl, whisk together flour, baking powder, and salt. Gradually add to wet ingredients, stirring until a thick dough forms.

Divide dough into three portions. Keep one plain, adding red food coloring to the second bowl and blue to the third. Mix until colors are vibrant.

Cover bowls with plastic wrap and refrigerate for at least 1 hour.

Preheat your oven to 350°F (175°C) and line baking sheets with parchment paper.

Scoop 1-inch portions of colored dough, rolling into balls. Combine red and blue for marbled cookies. Roll in powdered sugar.

Place dough balls on baking sheets and bake for 10-12 minutes until puffed and cracked.

Let cool on the baking sheet for 2-3 minutes, then transfer to wire racks to cool completely.