I've heard of a slight greenish cast on some ND filters and some center filters (essentially graduated ND filters), but had not heard of it on polarizers. The slight cast on ND filters is occasionally mentioned in the context of shooting colour films but is not pronounced enough to have any material effect on B&W films. This of course depends on how green it is. The very slight colour cast I'm talking about is barely noticable (if at all) to the eye, so your case might be a little different since it seems to be a fairly obvious green colour. Like any other colour, the more saturated it is the more of a filtering effect it will have on incoming light. So if it is really quite green, you'd have a non-neutral combination polarizer-green filter. Obviously the specific hue makes a difference in the wavelenghts it will absorb/pass.