I have done the "window test" with a grey 7" of GIAC and it does indeed turn green after some time in the sunlight. Along with the color, the quality of the image also changes and appears a bit washed out. I then compared it to my Australian 7", which was intentionally released with a green tint, and the shade of green and image quality vary too much for me to believe the green UK version was intentional. I'm with IR and believe the 7" version with the 12" tracklisting is the only real misprint.
So am I.