It is nigh impossible that stones in Scotland would be glacial erratics originating in Greenland. For one thing, there is no way anything would be carried across an ocean basin and up the other side (much less across the Mid-Atlantic Ridge). The British Isles also were never connected to Greenland in the past (before Pangea split apart). For isolated deposits near harbors, there is always the possibility of ship ballast being dumped, though the likelihood is very slight that any such rock would have come from Greenland (a Viking wreck?). Occam's Razor would have you look for something similar that is closer to home.
The suggestion of vesuvianite is an interesting possibility. There is some metamorphosed vesuvianite in limestone deposits in Aberdeenshire and Skye, though I haven't seen anything as large or similar in appearance as your pieces from there (just small, brown crystals). Worth considering, however.
I'm also wondering whether what you've described is chatoyancy (a shifting inner glow/line caused by inclusions, lamellae, etc.) or pleochroism (a shift of color depending on how the crystal is oriented)?