I'm doing my first open book cake for this weekend. I'm making it out of two 9x13" cakes.

One side is lemon cake with raspberry filling. The other side is chocolate cake with fudge and raspberry filling.

It's a no-brainer for a lemon buttercream on the lemon cake...it's white so no problem.

The problem is the other side. I have no idea what flavor buttercream I should use, that's the same color (white) as the other side.

Anyone have any ideas? Should I make both sides the same?

Vanilla or almond would be good.

y'know i would split the difference and use all vanilla icing -- if the cake is already lemon -- good enough -- if you use real vanilla in the icing -- and that is important it will be a different shade than the lemon icing -- so i would opt for a uniform look --

well you could actually put a fondant sheet on the top as if it were the top page and then you've just got a bit of color difference around the edges only -- and if you use the times of a fork or whatever to make the edges look like the pages/edges of a book -- you could get away with it as lemon icing on one side and vanilla on the other --

oh god that hurt my head

White chocolate, lime coconut mousse, Irish cream, vanilla. ..but as k8 said, a slight difference in colour might be noticeable. 

Yes, I'm leaning more towards vanilla icing at this point. My client doesn't want any fondant, so it needs to be all buttercream. 

Hmmm....white chocolate buttercream? I've never made nor tasted that before...

Thank you for your input!