First of all, I unfortunately do not have a digital camera or a scanner for "proof" of this, so I apologize in advance.
I just got back from the local Target, who had stocked a case of the "Bly and Gree and ten more pegwamers" assortment. I needed to get a different Gree since, as I stated earlier, mine's nose stripe thing was off-center and it was bugging me more and more every time I looked at it.
So anyway, I got home and more or less switched the head on the new one onto the first Gree I got (the new one's left knee joint was kind of loose) and it was only when I was looking at the belt that I noticed this: My first Gree (sounds like a Fisher Price commercial, don't it?) has a completely different detailing on his body when compared to the one I got today.
I don't know how to best explain the differences, as they aren't red/green Clone Commander obvious, but the most vivid area where this is very noticable is on the chest. The first Gree has a kind of "fuzziness" (as if he's been in some battles and the black paint is chipping at the edge of the lines and it has some additional "mud" on it; the second Gree's chest is totally clean, has straight lines, and no chipping.
This goes beyond a simple "bad" paintjob on the first one I got; it's obviously something that has been changed from the first to the second version. The first version seems to be much more realistically detailed than the second one, which although a bit dirty, looks like he just painted his armor recently and saw no battles. I guess if I had to compare it to something, I'd say it's along the lines of the #50 Anakin Original Recipe vs. Extra Crispy, but a lot more noticable.
Again, sorry for the lack of technology to put this into pictures, but I thought I'd throw this out there so if someone else had two Grees, they could compare them to see what they had.