Sometimes getting across exactly what you want isn't easy. I think she had a white cake mix (hence the "term" vanilla"). I'm sure she's already made it by now. I asked all the pertinent questions and this is as close as any of us could come to what she wanted. A Red Velvet cake is made with flour, cocoa (which makes it dark) and red food coloring. So you can actually start out with a white cake mix, or yellow cake mix, if you wanted to. We worked really hard to get any information that would be beneficial.
The key here is you can only give as much information to someone as long as they understand the questions. So, logically, she actually was making a Red Velvet Cake - I did ask but never got a difinitive answer - she just wanted to know when to ADD the red dye and how much. So all I could do is post a recipe that used a white/yellow cake mix for her to go by. I know she used the term vanilla - but that could have been a term used for the actual color - like vanilla versus chocolate. And I don't know of a vanilla cake that actually uses red food coloring - so the vanilla was just a word for the color of the mix. And if she had absolutely no recipe to go by most people, especially those that don't bake and haven't had the access to cookbooks, etc., would never know that a Red Velvet Cake gets its darkness just from cocoa - NOT a chocolate cake mix - so she didn't know to even ask about the cocoa - because common sense would tell you to add the red food coloring the same time as the cocoa. But if all she really wanted to do was just color a cake red then the directions I posted should have helped her too.