Ombre Christmas Tree Cupcakes
Make the frosting: In the bowl of a stand mixer, beat the powdered sugar and butter, starting on low speed and working your way up to high, until incorporated, about 1 minute. Add the milk and beat on high until smooth and fluffy, 30 seconds to 1 minute more.
Set aside ¼ cup of frosting aside. Divide the remaining frosting among four bowls; leave one bowl white. In a second bowl, add 10 to 12 drops green food coloring and mix well with a spatula until no streaks remain. In the third bowl, add 5 to 6 drops green food coloring and mix well. In the fourth bowl, add three to 4 drops green food coloring and mix well. Adjust colors as needed. To the reserved ¼ cup frosting, add 3 to 4 drops golden-yellow food coloring; mix well.
On a large cutting board, tray, or flat serving platter, arrange the cupcakes in the shape of a Christmas tree, starting with one row of 5 cupcakes and decreasing the number of cupcakes as you move upward. Above the top, place one cupcake to make the star. At the bottom, place two cupcakes in the center to make a base.