In a large bowl, whisk together the flour and baking powder.
Cream the softened butter and granulated sugar until light and fluffy.
Add the egg and vanilla extract to the butter-sugar mixture, mixing until combined.
Gradually add the flour mixture to the wet ingredients, mixing until a soft dough forms.
Divide the dough into three equal portions.
Color one portion with cocoa powder, and the other two with gel food coloring.
Roll each colored dough into rectangles on parchment paper.
Layer the doughs on top of each other, gently pressing to adhere.
Tightly roll the layered dough into a log, then wrap it in plastic wrap.
Preheat the oven to 350°F (175°C).
Slice the chilled log into ¼-inch thick rounds and place them on a baking sheet.
Bake for 10-12 minutes or until the edges are lightly golden.
