Striped Meisterstück pens did indeed exist. From the older Meisterstück generation, a 142 with a green striped body and a 144 with a grey striped body are among those documented. Pieces like these are rare and much wanted by collectors, and copies and fantasy versions turn up correspondingly often.
A conspicuously green marbled body that otherwise shows the design language of a modern Meisterstück is in all likelihood a fake. The giveaways lie in the details, which can be checked well on close-up photographs: on crude fakes the star on the cap top is poorly formed and looks more like a flower than an even six-pointed star, the cap rings are imprecisely made or wrongly lettered, and the nib engraving differs from the original in its lettering and its arrangement. Comparison with documented originals of the same model is therefore advisable before any purchase, since combinations of colour and shape that Montblanc never made rule a pen out for certain.