Yes, it is just a 2 color scheme. The Light grey on the verticle surfaces continues down to the bottom (belly) of the Aircraft.
The paint weathers horribly on these aircraft. The finish gets torn up pretty badly by exhaust from the T-64's, grease from the rotor heads, leaks from hydraulics, fuel, and oil. The greatest damage to the paint comes from the maintenance crews. The hand and foot holds usually show signs of chipping. The paint seems to get permeated by dirt, and the aircraft actually seems to get darker as time goes on. Markings such as the Modex (CJ on the Academy Model) and the Aircraft number (08) are often painted over and repainted as aircraft are moved from squadron to squadron. There is often lighter grey paint square under these markings. The Word "MARINES" and the Star and Bars is applied in a civilian contracted paint hanger durring Depot Level Rework, and are grey. Squadron and aircraft specific markins are applied by the squadron upon delivery to the unit and are black.
I used Tamiya colors when I built a 1/72 CH-53E a couple of years ago. I found XF-20 Medium Grey and XF-23 Light Blue to be a good match for the big pig's color scheme.
Check out my photobucket spot for reference pics of the 53 and to check out the colors I used on that 72nd scale 53.
http://smg.photobucket.com/albums/v491/ridleusmc/
Semper Fi,
Chris