Hi Gary
Here some comments as you requested
Uniforms & camo.
Youre right: Most of uniform were just green but to help differentiate you COULD follow this guideline.
-Camo for ROK Marines shown in pic 1 (Pics are numbered left to right)
-Camo for ARVN can be different. Some Bns used camo as in pic 2, other Bns used special forces tiger strip as pic 3. Pic 3 can also be used as unofficial but quite common camo for US Special Forces, such as Green Berets and LRRP
- The green uniform with red beret you used for ARVN Rangers should be used for ARVN Airborne troops instead. The same green tone but with helmet should be used for standard ARVN infantry.
-US infantry and USMC should use slightly different green + Flak vest and camouflaged helmet (less common in ARVN)
Weapons
ARVN infantry should be in two versions with M1 carabine (early) and with M16Assault rifle (later)
ARVN rangers, Airborne troops and ROK marines should be with M16 only
US troops should be with M16 (even if they used M14 and other rifles in early stages of war)
Please note M203 grenade launcher was quite uncommon in Vietnam. It was actually introduced in early 70s so M16 without GL is a more accurate choice.
If you want to fit your units with grenade launchers then you should use M79 instead but this would require a different animation.
Other weapons that you might want to consider are M3 grease gun SMG to equip US/ARVN Military police units or ARVN CIDG (see below) and machine guns / mortars/ RPG (for NVA/Vietcong)
Other Units
Too many
Any decision is up to you. Here is just a list you can use to pick up what you want:
-US/ ARVN Combat engineers (same as standard infantry but with a couple more animations such as build and pillage/breach)
-NVA/VC sappers. These are elite assault troops with some abilities to break obstacles. Sometimes female. See pic 4
-US/ARVN heavy MG and or mortars
-NVA/VC heavy MG, mortars
-NVA/VC with RPG (same as infantrymen you did before but with different weapons
-US/ARVN MP (with SMG and Military dog, black jacket and helmet)
-ARVN CIDG (Civilian Irregular Defense Groups)
-VC local force. Black uniform, no helmet (use SE asia farmer hat instead if you want), old rifle. See pic 5
Please let me know if you need any further detail on specific units.
Also
check your PM