Preheat oven to 350 degrees Fahrenheit.
Grease and flour 3 (8-inch) cake pans.
In a mixing bowl, cream (beat together vigorously) sugar, butter, oil, and eggs until light and fluffy.
I a small bowl, combine food coloring and cocoa, and mix to a paste.Add this to the creamed mixture.
In another mixing bowl, mix together flour and salt. (Sift this mixture 4 times).
In a bowl, combine buttermilk and vanilla.
In a small bowl, mix together baking soda and vinegar.
With your mixer off, add about 1/3 of the flour. Turn the mixer on low and run until combined with the creamed mixture, then add about 1/2 of the buttermilk, then another 1/3 of the flour, the rest of the buttermilk, and ending with the remaining flour. Add the vinegar and soda mixture and blend until just combined.
Divide the batter between the 3 prepared cake pans. Bake for 30 minutes.
Remove and place on cooling racks. Cool in the pans for 10 minutes, then remove from the pans. Cool completely.
In a stand mixer, combine butter and cream cheese, and beat until light and fluffy, this will take a while.
Meanwhile, melt chocolate in microwave and let cool slightly.
Add chocolate and orange juice simultaneously to the creamed mixture, and beat until frosting foirms.
Let frosting stiffen some in the refrigerator. Spread on one layer, sprinkle chopped nuts on frosting, then top with second layer , continue until all three layers are frosted on top and sprinkled with nuts. Frost top and sides of cake and sprinkle with chopped nuts.