Cream together your butter and sugar using a hand mixer. Add the vanilla, then each egg individually, giving time for the each egg to incorporate fully.
Add your food coloring. Remember that you'll be fighting against the darkness of the cocoa powder, so start with 4 drops and add more if your red needs more pop.
Add the oil, salt, and cocoa powder, then add your flour. Be careful not to overmix the batter when you add the flour mixture. Mix it until the flour is just incorporated.