Not so sure Contract Dog, although confusion could be caused due to UN-xxxx registered aircraft (for the majority white and of Sovet origin) and similar aircraft operated by the Sudanese airforce for military operations.
But fairly new Mi-171s, completly white, without country roundel or national registration have been seen in Sundan. Bur more damaging are pictures of a An-26, it is registered -26562, thus without the country marking. Its completly white and has been used for bombing runs. This particular aircraft has UN Markings on its wing, whether intentionally or not. See the link, they are on page 30 and 31.
Link to the UN doc with the pictures:
http://www.sudantribune.com/IMG/pdf/...UDAN_PANEL.pdf
hope it works,