Not a highly photographed vehicle apparently...
This was all that Google returned, but the first one is in the Balkans, 1942, don't know about the second one. Looks like standard Italian overall Sand Yellow (FS20260 or RAL 1002), which looks something like this;
What this translates into Tamiya or Humbrol paint numbers I don't know. Find something that comes close and go with that. After weathering, it won't really matter.
The same for the Fiat, war-time photos of this car are scarce. Personally, I doubt they would have bothered with additional camouflage, but....never say never. I've seen plenty of other staff cars with elaborate paint schemes.
Good luck!