We didn't paint the magazines green or any colour except black. The crunchies used to daub their rifles and shotguns with green and yellow paint when on ops but they didn't stay that way for long I have to say. When they came into the Armourers shops they had to be in service condition when they left - within reason. The trouble with a lot of the oil based paints and the spirit based stuff is if wasn't baked on hard was that the insect repellent would just soften it and it'd come off easily
The short serial number is just that. A short 3 figure number that is insignificant.
I would imagine that the magazine will just be an ex Indian one taken from another rifle