Mix sugar, salt and shortening together until fluffy. Add eggs, on at a time; beat well after each addition.
Mix coloring and cocoa. Add to sugar mixture, beating well. Add buttermilk and flour alternately, beating well after each addition. Mix baking soda and vinegar and fold into mixture.
Bake in three 9- inch greased and floured pans at 350 degrees for 20 to 25 minutes. The cake is done when it pulls away from the sides of the pan. Do not over bake. Let cake cool in pans or on racks for 10 minutes.