Beat the butter and sugar with an electric mixer until light and fluffy. Add the vanilla extract and eggs 1 at a time, beating until combined.
In a separate bowl, combine the flour, baking soda and salt. Add this to the batter in two batches, alternating with the buttermilk. Add the green food colouring and mix until combined.
Line a mini cupcake pan with green cupcake liners and fill the pan ¾ of the way full with the batter.
Bake at 350F for 15 minutes, or until a skewer inserted into the cupcakes comes out clean. Allow the cupcakes to cool completely.