If you look at the cowl of my Rufe in my signature pic, you'll see what Aeromaster marketed as cowl blue/black. I believe that White Ensign Models now has this (along with many other IJN/IJA aircraft colors.
For anyone building WW II Japanese aircraft, I recommend this site highly:
http://www.j-aircraft.com
In the "Reference" section, you'll find a lot of info on the China air war (where the type 11 was used), along with a page of notes dealing with the issues with Tamiya's 1/32 Zeke.
Hope this helps.