You are rigth. The more I study the picure the more I think the did a wonderful job.
The paint was carefuly applied -looks like that they used a spray gun-. They even took care to paint the interior!
I have no clue about from where the paint came from. Itīs a ligther OD colour than the FS green used in the plane. In fact, I donīt think they used airplane paint due chemical incompatibilities -??- or, in any case, if they had had stock of aviation colours enough, they better had used it in those birds. Notice the heavy damage on the paint of the background aircraft.
Itīs fascinating how even the simplest pic can turn modellers life into a nightmare!