The precious resin versions of the Meisterstück are available in black and in Bordeaux, the Bohème exclusively in black. Marbled writing instruments in green, blue or grey date from the 1940s; they do not exist in the current range. Meisterstück ballpoint pens are not offered in green, yellow, white or similar colour combinations.
At Montblanc, brightly coloured writing instruments belong to other lines, such as Noblesse and Generation, which are indeed available in yellow, orange or green, but not to the Meisterstück pens. A green marbled or yellow Meisterstück ballpoint pen is therefore very probably a counterfeit. It is also typical of such fakes that a coloured barrel is combined with a large black cap.
Black writing instruments cannot, in the nature of things, be checked by their colour and are therefore harder to identify as counterfeits.