In a medium bowl, combine flour with cocoa powder. Set aside. In a separate mixing bowl, with a hand mixer, cream the butter and sugar until light and fluffy. Add egg and vanilla extract, and beat again.
Use a medium cookie scoop to drop the dough onto the lined baking sheet, leaving two inches between each cookie. Bake for 10 minutes, or until the cookies are set and the tops are no longer shiny/glossy.
If needed, add a small amount of milk to the frosting to get it to the perfect piping consistency. Divide the frosting in half into two separate bowls. Use food coloring to tint one bowl yellow, and the other with orange color.
To combine the frostings, lay out two pieces of plastic wrap. Add the frosting to the wrap, and then roll it up into a tube shape, twisting the ends to seal. Snip off one of the twisted ends from each tube.