"Whoever dared paint markings on a plane's wing was a swine," said one of Pierre Clostermann's comrades the night of the 8th of May, 1945. Latest reports from Sudan suggest you can do pretty well painting them out, too. The Sudanese government has been caught using various Antonov-26 aircraft to bomb villages in Darfur, having repainted them to look like the UN's food airlift.
This raises the question, of course, of whether some of the "UN" aircraft are actually UN-registry ones, that is to say Kazakhstan. Viktor Bout's airlines have relied on this coincidence before, taking advantage of the fact the UN World Food Programme is often operating in the same places with the same rugged Soviet planes, chartered from similarly dubious owners.
So far, none of these have been spotted. The UNSC report, for example, mentions one with a Sudanese civil registration ST-ZZZ, a fake. The plane is probably serial no. 57303506, which used to be registered in Russia as RA-26563 before its sale to Sudan. It has occasionally been reported as "UN-26563" masquerading as a UN aircraft. (That registration does not exist either.) There's a photo, as well as a copy of the report , here.)
It's the stuff. Sudan has been a significant market for both Viktor Bout and Britain's own friendly local warzone airline Avient, and here's something interesting. In the photograph of a gaggle of Mi24 (Hind) attack helicopters on the flight line at El Fasher, you can see the nose of an aircraft in Air West colours. Air West (ICAO: AWZ) is also known as East-West Cargo, and is a company on the UN Security Council asset freeze list. A scan of its aircraft roster shows planes swapping in and out with Irbis Air Co, GST Air Co, and BGIA, including a Yak-42 that was also caught operating into Iraq from Dubai in mid-2004.
Frustratingly, the UN also took photos of an Il-76 unloading armed Land Cruisers there, but it's impossible to make out the registration. It doesn't look like any of the Airwest ones, though, nor GST, neither is it Avient's Z-WTV.