For the cupcakes, preheat oven to 350°F (180°C). Prepare cake mix as directed on package, adding vanilla. Remove about 1 3/4 cups (425ml) of the batter to small bowl; set aside. Add green food colour to remaining batter. Spoon green tinted batter into 16 paper-lined muffin cups. Spoon remaining untinted batter into 8 paper-lined muffin cups.