Add the flour, baking powder, and salt to a large mixing bowl. Stir with a fork to combine and set aside.

In a separate large mixing bowl, cream together the butter and sugars using a mixer. Beat until smooth.

Add the egg and vanilla and mix again until smooth.

Fold in the dry ingredients, half at a time, and mix until a thick and smooth dough forms.

Divide the dough into three equal parts. Color one part green, another red, and leave the third white. Roll each out flat about ¼ inch thick.

Layer the colored doughs on top of each other (red - white - green). Use a pizza cutter to cut out a rectangular shape, about 9x13 inches.

Carefully roll the layered dough into a log, pinching the end to seal. Wrap in plastic wrap and chill for 2 hours.

Preheat the oven to 350°F near the end of the chilling period.

Unwrap the dough and slice into ½ inch thick cookies. Place on a parchment-lined baking sheet.

Bake for 13 to 15 minutes or until just set. Cool on the baking sheet for 1 minute, then transfer to a wire rack to cool completely.