Yes I have noticed that, for at least a month or more.
Not all sites went with the green, some have stayed
with the black flag, others green with a black flag, others
green with UBL in the center, others green with GIM logo and
still others green with 2 rifles crossed, or hands grasped, etc.
IN MY SPECULATIVE OPINION, it's just regrouping. Just
like cats pee on certain spots to mark their territories,
just like gang bangers who mark their turfs with graffiti;
well the jihad or islamists-extremists or supporters of jihad
or just general interesting sites have gone green to mark their new groupings.
Yes, I've noticed it's been building up gradually the last couple of weeks or so, with more and more of the sites going green. I do remember reading that the Koran shown in one color means one thing, and then seeing it another color means something else. So a change is significant.