I am going to make an ombre birthday cake for a friend of mine this week (similar to this one http://www.flickr.com/photos/clapanuelos/6781447298/ ). I am planning to use the "doctored" box mix recipe found here http://cakecentral.com/recipe/cake-mix-extender with a white box mix to ensure that I start with a really white base (I have never tried this recipe, though, and am open to other suggestions).

The ombre technique seems pretty straightforward (make the mix, separate into bowls, add different amounts of coloring, and bake in separate pans) but I want to try doing sort of an ombre effect with the flavor too, if that makes sense. I am planning to have the gradient go from white to purple and was thinking about adding progressive amounts of cocoa powder to the bottom two or three layers. I do not want this to take away from the coloring (I'd like the purple gradient to be as seamless as possible) but I am using a white swiss meringue buttercream and am concerned that the cake will be too bland without adding flavoring.

Has anyone tried this? If so, any suggestions for the amount of cocoa powder to use? Or thoughts on a different flavor or technique that would work better? The layers are going to be 6" rounds and I am planning to have four layers total. Any input would be appreciated!

It has to be different shades of purple? The brown will probably alter the shades of purple, if only you could do a shade of yellow or brown that can blend more with the cocoa shades.

You're adding this to the cake itself? I don't think that would make the flavour better, and I don't think there would be any way to avoid it affecting the colour. Why not use more vanilla or another clear flavouring if you think the cake will lack flavour?

It sounds too pretty to ruin!

Use something like blueberry flavour--the LorAnn is colourless and tastes good. The flavour should match the general colour or else people will think there is something "off" about the cake.