I actually asked this question a few months ago.
According to roster expert Bill Gingrich, there are just three GRS gray schemes.
Ph.1 Solid gray body, frame, trucks and fuel tank with a broken orange stripe around the locomotive. The "Big G" logo on both sides, And the road name spelled out on the Hood sides. A large number below the window on the cab. Orange/white striped pilot.
Ph.2 Same as Ph.1 except the pilot was solid orange.
Ph.3 Same as Ph.2 except the road name was on the hood was replaced by "Guilford Rail System" and the large number under the cab window became a small number and reporting marks. Post 2001 repaints got an American Flag on the cab.
FRA mandated frame striping has been applied to all active locomotives (Ph.3 and 2) no examples of Ph.1 still exist all locomotives have solid orange pilots/plows. I beleive only 2-3 examples of Ph.2 still exist. #334 and 621 come to mind.
As Newpylong pointed out, there were several variations on the same theme. For example, The SD26's had the G and the road name reversed on the engineer's side-the "G" was close to the cab and the "ST" was under the DB blister. This was corrected when the locomotives came in for a second paint job. Also, Oneonta seemed to always get the short end of the stick. Their paint was always lighter than at Waterville, and the quality of the job was never quite up to par with a job done at Waterville, this was do to a mass of locomotives to paint and a lack of time/material not poor workmanship.
Just looked at your pictures again. The first one (BM 200) is in GRS Ph.2 paint. The BM GP38-2's were different in that most of the fleet had white number boards with black numbers (still true today) THe second picture there is only one paint phase, all three locomotives are in Ph.1 paint. The stripe does not wrap all the way around on the lead unit and while it is a little odd, if you look at other locomotives in any gray you will notice that the stripe does not real come up far on the engineer's side. And the last one MEC 317 is indeed in Ph.3, notice the FRA required striping on the frame, but the locomotive was last painted before 2001 as there is no flag.
Found the thread I started a while back-
http://www.railroad.net/forums/viewtopi ... 55&t=62037
Hope that helps