I was looking for online pics of the CCKW-352 shortwheelbase truck, and found a website on the 2-1/2 tonners. This particualr page set is a copy of a WW2 markings TM for these vehicles, with pages of examples, and placement of national and service markings in US use. Other parts of this basic website, which is aimed at the vehicle collector restorer, show wartime pics of interest. One shows a stopped convoy (likely Redball Express) with several of the trucks having the rear "bumpers" painted white (for night convoy use?).
Here's the markings TM site:
http://www.cckw.org/tm9-850.htm
Dan