Traditionally, no. If you want a traditional red velvet cake, then use the natural cocoa powder and buttermilk/vinegar combo to get that slight red color.  However, most modern recipes rely on food coloring to dye the batter red, so you can substitute any color for the red. For example, blue velvet is another popular kind of dessert. Heck, you could do green for St. Patrick’s Day Celebrations!  Do keep in mind that some colors may be more appetizing than others, so proceed with caution here :)