In a mixing bowl, cream the sugar and butter, beat until light and fluffy.
Add the eggs one at a time and mix well after each addition.
Mix cocoa and food coloring together and then add to sugar mixture; mix well. Sift together flour and salt.
Add flour mixture to the creamed mixture alternately with buttermilk. Blend in vanilla. In a small bowl, combine baking soda and vinegar and add to mixture.
Pour batter into three 8-inch round greased and floured pans.
Bake for 20 to 25 minutes, or until a toothpick inserted into the center comes out clean.
Remove from heat and cool completely before frosting.
Blend cream cheese and butter together in a mixing bowl.
Add marshmallows and sugar and blend. Fold in coconut and nuts.
Spread between layers and on top and sides of cooled cake.