My GUESS is white means a past Civil Defense assignment.
I'm not sure if U.S. Army vehicles were painted for UN work. Often times, the UN peacekeepers were from countries like Canada or Sweden, not the U.S. (for political..to look more "independent" .) Now if it were a Canadian M38A1, that could be a real possibility.
Also, it could be from a post Federal government ownership...given to a county or city. Police, sheriff...I've even seen white fire trucks.
Blue would probably mean Air Force or later Civil Air Patrol use. My guess is the CAP possibly utilized more Jeeps than the active duty Air Force ever did, getting them from Army or National Guard (as well as Air Force) surplus.