Cream butter and sugar until very light and fluffy. Add eggs, one at a time, beating well after each addition. Then add both extract and coloring. Mix flour and cocoa, be sure all cocoa lumps are mashed; then add this to the butter mixture. Stir real well; add buttermilk, again mixing well. Combine soda and vinegar in a small cup and pour over batter mixture; mix real well. Pour in pans. Bake at 350 degrees for 25 minutes. Let cake cook completely before frosting.