In a large mixing bowl, whisk together the flour, baking powder, salt and baking soda. Set aside.
In the bowl of a stand mixer fitted with a paddle attachment, beat together the butter, brown sugar and sugar on high speed for 1 minute or until smooth and creamy.
Next add in the eggs, milk, vanilla and butter extract. Beat together for 30 seconds.
Then add in the flour mixture and bring together until fully incorporated being careful to not overmix.
Divide the dough in half and place each half in a separate bowl. Then add red food coloring to one bowl and green food coloring to the other bowl. Mix well until all of the dough is evenly colored.
Transfer each section of dough to two separate, large pieces of plastic wrap. Shape each section of dough into a 5x5” square. Wrap tightly with plastic wrap and place both squares into the refrigerator to chill for 30 minutes.
Once the dough has chilled, remove the plastic wrap, stack the dough squares on top of each other so that they are perfectly aligned.
Place the dough onto a lightly floured surface. Gently flour the top of the dough. Use a rolling pin to roll the square out into a rectangle about 9” wide and 18-20” long. Tightly roll the dough up into a log starting on the long end.
Tightly wrap the log with plastic wrap and place it into the fridge to chill for at least 1 hour.
Once the dough log has chilled, preheat the oven to 350 F. Line a baking sheet with parchment paper.
Unwrap the plastic wrap from around the dough log. Place the log onto a cutting board and slice ½” wide cookies. You should have 18-20 cookies.
Place the cookies onto the prepared baking sheet leaving at least 3” of space between each cookie for spreading. For a full baking sheet, you can fit 9 cookies and for a half baking sheet you can fit 5 cookies max.
Place the baking sheet into the oven to bake for 18-20 minutes. The cookies should not be browned around the edges. The edges will feel set and the rest of the cookie will feel soft.
Remove the baking sheet from the oven and place the cookies onto a cooling rack to cool completely. Bake the remaining cookies in the same manner.
Allow the cookies to cool for at least 10 minutes before serving as this allows the cookies to set up.