Wow, that's just great! I love the work you did to this one. Also the diorama start is wonderful!
For the colours (hardedged, I think), have a look at this link. The mixes, I'm afraid, are only in Humbrols. Maybe you have a conversion chart? Anyway, in the dusty plains of China, I suppose most of the Tractor will be... well... dusty.
As for the camo scheme, I will send you by mail a rather good profile, as well as a couple of pics you possibly have not found on the net.
I'm looking forward to seeing more of this beauty!