Points to consider:
- As mentioned, they talk about it being green in the film, and since dialog is not likely to factor in color timing, you can be certain that it IS green-tinted. Now, that could mean (as it would seem from the various display images folks have taken) that it's a grey base fabric with a 5% green dye added- it'll still look mostly grey, but will be tinted enough for people to be able to call it green.
- Ignore ALL movies stills AND "behind the scenes" photos as to what color it really is. Even the BTS shots have been doctored heavily even if it's not apparent.
- The best way (besides actually seeing in person) right now to gauge the color is by looking at random cell phone snaps. Cell phones are set to take fairly neutral images that have a broad color range and, while they may enhance some things, will not heavily tint anything unless you have them set to a filter.
- One thing you can do is take a selection of cell photos, import them into Photoshop and do some color analysis to get pretty close to the correct tint.
I also had a thought about the lapels and collar. I think it's cheap long-haired polyester fleece, not regular "fashion fur" which is usually too fine or faux shearling. Fleece fits with the overall "cheap" look (since K isn't rich) and looks very much like that. Fleece has that fuzzy "shredded wool" look right from the start.
A- Anything could factor into the color grade, they could
easily make his jacket "look more green" in a scene where someone actually says it's green.
B- Any image that's released has been through photoshop, so yeah.
C- Cell phones images vary pretty heavily, you can find hot debates about this all over the internet. I wouldn't call this "the best" way. Not to mention convention style display lighting is usually atrocious, and includes all kinds of different color temp lighting, mixed together, and crappy little bulbs... Don't get me started.
D- I suppose you could do this, but I don't see how it would help you determine what color you want your jacket to be, also the lighting where your photo was taken vs. Deakins, the color space that the film was shot in, vs. your cell phone, vs. your monitor, vs. how you handle the image vs. whatever they graded it in, baselight or whatever... Too many variables. This isn't a scientific process.
On top of all of this, we don't know how many jackets there are. There could be greener ones, and greyer ones.