Preheat oven to 350°F.
In a mixer with a paddle attachment, mix the oil, sugar and eggs until creamy. In a separate small bowl, combine the cocoa powder and food coloring, and stir. Once you have a thick paste, add it to the mixer.
In a medium bowl, combine the flour and salt with a whisk and set aside. In a liquid measuring cup, combine the vanilla extract and buttermilk. Stir and set aside.
Add half of the buttermilk mixture to the mixer and stir on a low speed. Add half of the flour mixture and combine. Alternate this process with the remaining wet and dry ingredients. When all wet and dry ingredients have been combined in the mixer, fold in the baking soda and vinegar.