In a large bowl, combine flour, cocoa powder, baking powder, baking soda, and salt.
In a medium bowl, combine buttermilk, green food coloring, and vanilla.
In a large mixing bowl, beat sugar and butter until light and fluffy, about 3 minutes.
Add eggs, and beat until well-combined.
Add the dry ingredients and the buttermilk mixture to the mixing bowl, alternating.
Divide the batter evenly between two well-greased 8-inch round cake pans.
Bake at 350 degrees for about 25 minutes, or until the edges are golden, and a toothpick inserted near the center comes out clean.
Cool for 20 minutes in the pans before removing to wire racks to cool completely.
Using a serrated knife, level the tops of the cakes.
While the cakes cool, prepare and bake the cheesecake.