To answer a few questions and no doubt miss some.
The NVA used coloured ribbons as Carlos says. In the scene in Full Metal Jacket there is a NVA corpse in a chair. If you look at his shoulder he has the ribbons stitched on.
Gas masks. The CS Gas was initially used in an unplanned way as a Marine officer found a CS gas mortar in a crate and thought it would be useful in house clearance. When he asked the assembled Marines if they had their gas masks only a few said yes. However it worked and they developed the usage. We thought about a simple head sprue of Gas mask heads. Saves on painting faces
Helmet head bands were against Marine regs however there a lot of pictures of Marines with them on. The next sculpted batch will be without to balance the ratio....... however they do look cool.
Figure of the day;