Preheat oven to 400°F. Line a cookie sheet with parchment paper or silpat.
In the bowl of an electric mixer fitted with the paddle attachment, cream together the butter and sugar on low-medium speed (I set it to 4 on my KitchenAid).
In a small bowl, whisk together the egg and extract.
Scrape down the creamed butter from the sides of the bowl and add the egg mixture. Mix on low (I set it to 2 on my KitchenAid) until combined.
Add the flour and baking powder and mix on the lowest setting (I set it to "stir" on my KitchenAid).
Divide the dough into thirds.
Tint each third with a color gel. Begin with a little bit of color and simply add more until the desired color is reached.
Working in batches, create a 3x3 square pattern of alternating colors (see example in post).
Roll out the dough to about ¼” thick and cut out leaves where the colors intersect. Transfer to the prepared cookie sheet, spacing about ½-1” apart.
Bake for 7-9 minutes.
Maintain the scraps as sheets and patch them together.