Glenn,
I am building a Tamiya A6M2 type 21 also, and the colors are very confusing. I went straight to the experts for the answer. HERE is a thread I started over on LSP on this very topic. On page 2 are the mixes by Greg Springer for both the Mitsubishi as well as Nakajima built Zeros (and yes there was a difference). I used Tamiya XF-71 for my interior color and I think it turned out fine. I will use the "Springer Mix" for my exterior colors.
HTH,
David