Combine creamy peach icing color and brown to get peach color shown for brains. Combine red-red, rose and brown to get dark red color shown for intestines. Tint 1 cup of white icing peach using color combination. Tint 1 cup white icing dark red using combination. Prepare three decorating bags, one with tip 4 and peach brain color, one with tip 1A and peach brain color, plus one with tip 8 and dark red intestine color.