Preheat your oven to 350°F (175°C) and line a muffin tin with 12 cupcake liners.
Prepare the vanilla cake mix according to the box instructions. Divide the batter evenly between the liners, filling each one about ¾ full.
Bake for 18–22 minutes, or until a toothpick inserted in the center comes out clean. Let the cupcakes cool completely before decorating.
In a small bowl, stir green gel food coloring into the vanilla frosting until you get a nice tree-green color. Chill the frosting for 10–15 minutes if it feels too soft.
Spoon the frosting into a piping bag fitted with a large star tip. Pipe tall swirls on top of each cupcake to look like a Christmas tree.
While the frosting is still soft, add sprinkles and press a gold star topper onto each cupcake. Serve or refrigerate until ready to enjoy.