Cracking work Ash! I'd love to see a colour guide as to how you've gotten such a great palette on these models.
For the most part these blokes are all wearing the same kits so are going to look some what similar;
Main base colours (Vallejo):
BDUs (trousers, sleeves, shirt collar, bottom of shirt/jacket below flak jacket) : US Dark Green, shaded with washes and highlighted with base colour and some Panzer Aces Splinter Strips, then some Khaki.
Flak jackets: Most are wearing what looks to be USMC M-1955 fragmentation protective vest. I've seen pictures of these in every shade from Olive Green thought to a faded khaki. I went with the Khaki option just to differentiate between the vest and the uniform, but I think it would be hard to pick a tone in this range that was incorrect. If they all end up looking too similar I may go over a few with an Olive or drab wash.
Hooded Jackets: US Navy Nylon jacket; see quite a lot of these in period pictures, also the trousers. A mix of cam Olive, USA Olive Drab & Khaki should cover all the variations. They do look quite dark in a lot of the photos, but then it was raining.
T shirts: Some have just a T-shirt under their body armour, pictures show a lot of dark olive green ( cam Olive Green with a little black), but I don't think you can go wrong with any greenish or brownish colour.
Helmet covers: Mitchell Pattern, with a green leaf shaped pattern on one side and lighter 'duck hunter'ish' blotchy tan pattern on the other. I base coated the first with Russian Uniform, the second with Khaki then gave it a dry brush with Dark sand. Various brownish blotches on the light side and some dark green leaf shapes on the dark ( add a few twig shapes in a brown colour).
Boots: Black for the leather and Russian Uniform for the canvas works as a starting point.
Webbing: I went with Russian uniform or Khaki as a base. Just to break it up a bit. Entrenching tool covers, IFAK pouches & Gas-mask haversacks in Khaki; Water bottle pouches, backpacks and m-56 ammo pouches in Russian uniform. Then various washes and highlighting.
Bandoleers: Another shade of green, again can't really go wrong. I went with an olive shade (base) highlighted with Russian Uniform, just to lift them from the flak jackets.