What is the difference between Devil's Food and Chocolate cake?
PracticallyEdible has a nice description of Devil's Food Cake.

Originally, Devil's Food Cake had a medium dense texture.  The colour had a reddish tint that was probably caused by baking soda reacting with cocoa powder.  In fact, I have an old cookbook (The Day by Day Cook Book, 1939) that contains a recipe for Red Devil's Food Cake.  This recipe calls for 2 oz. unsweetened chocolate and 1 tsp. of baking soda.