Preheat oven to 325°F. Grease 3 9-inch round cake pans.
In a stand mixer with whisk attachment, mix flour, sugar, cocoa powder, baking soda, and salt on low. Gradually add oil and buttermilk.
Increase speed to medium-low; add eggs one at a time, scraping the bowl after each. Slowly add coffee, vanilla, vinegar, and food coloring. Mix until just combined, avoiding overmixing.
Divide batter evenly among pans. Bake 20-27 minutes until a toothpick comes out clean. Don't overbake.
Cool in pans for 10 minutes, then invert onto wire racks to cool completely. Cover lightly to prevent drying.