Somewhere I remember reading that Japanese flex color codes were the same as North American codes (black=live, white=neutral, green=earth).
In fact, yes! I remember where I read it! It was in a catalog for some company that supplies "International" power cords (Panel Components Corporation). The flex that this company sells for the Japanese market is North American color-coded.
Although considering how the USA is supposed to be switching to harmonized cordage, maybe Japan will do the same thing eventually (when we're all dead?)
Ragnar, I'd suggest replacing that power cord with a modern one...if only to prevent confusion for any future owners hooking the green conductor to earth....