During the Vietnam war, navigation was extremely difficult because the jungle has extremely limited view range, so it becomes difficult to locate landmarks.
In fact, there aren’t many landmarks at all. So even if sight range was further, there wasn’t much to see.
This resulted in colored smoke being extremely important for multiple reasons.
First, to allow friendly aircraft to locate soldiers who can’t provide exact locations, and second to give forward air controllers (FAC) a point of reference for a-tt-ck. The FAC usually operated aircraft like the O-2 or OA-10.
A friendly would announce to the FAC he was about to pop smoke, without announcing the color. The FAC aircraft would then call out what color smoke he saw, and the ground troops would confirm or deny. That made it more difficult for the enemy to copy the color quickly.
The FAC could then either take information about where the friendly infantry needed strikes relative to their smoke, or the FAC could spot targets himself.
This allowed soldiers and pilots to operate closely without having precise coordinates. All they needed was to see the location of the smoke and the color.
And it also allowed helicopters to navigate to landing zones in confusing territory using the same basic principles. And made for a good song title by Jimmy Hendrix:
Source: Deactivated(Quora)
