No, the overall green could be either semi-gloss or flat, but semi-gloss went out when the camouflage came in. Camo is all flat, reduced reflectance being part of the camo effect.
The MERDC camo was introduced fleet-wide to all the services for tactical vehicles in c.1975 (except at Ft Hood where it was trialed for a couple or so years first), and was the standard camo scheme until the 383 3-colour came in early 80's.
While there are a fair number of older vehicles still sporting MERDC, anything still in MERDC probably hasn't been painted, except for touch ups, for almost 30 years, so it is all going to be very faded and "off spec" for colour.
My M185 was in the Summer Verdant scheme, but on most of it you would be hard pressed to tell, both greens having faded to a similar shade with a very slight blue tint to it. It looks like one green with some scurvy tan and grey (formerly black) patches.
Your desert trailer has the Gray Desert variation of the MERDC scheme, very faded and made somewhat confusing because of later touch ups with more brown paint giving something like a 5-colour effect.
If they were painted to the diagram, both trailers would have exactly the same pattern, only the colours would differ. Since the camo was often applied at a unit level, the actual patterns on vehicles can vary considerably from the diagrams in the manual.
Clear as mud?
Cheers
PS: remember, in all things military, there are always exceptions to the rule, nothing is absolute! For example- I remember seeing a Marine M151 on Camp Pendleton (c1979) in MERDC camo, but with all the lettering carefully done in yellow. The yellow lettering was supposed to go out with the overall Marine green.
) The correct color would have been either the # 24052 Semi Gloss forest green or #34052 lusterless forest green. 
