When I was a young driver it didn't matter what colour they were as long as they were clean and serviceable... we painted them with spray bombs of glossy black and with brushes loaded with the same green we were painting the trucks.
If the Sar'n't May-jah says paint the bloody things green, then green it is!
As for factory original it could well have been red as the the army really doesn't care. It would not be red so we wouldn't forget 'em tho'.
Cheers!
Mike
(In Ghana)