Cream shortening; gradually add sugar, beating well. Add eggs, one at a time, beating well after each addition. Combine water, red food coloring, and cocoa; add to creamed mixture, beating well.
Combine flour and salt; add to creamed mixture alternately with buttermilk, beginning and ending with flour mixture. Combine vinegar and soda, stirring well; stir into batter. Fold raisins into batter.
Pour batter into 2 greased and floured 9-inch round cake pans. Bake at 350° for 35 to 40 minutes or until a wooden pick inserted in center comes out clean. Cool in pans 10 minutes; remove layers from pans, and let cool completely. Spread frosting between layers and on top and sides of cooled cake.