What does the Injection Gun do?

I've been playing Lost Planet 2 for a few days now, and I just recently unlocked the Injection Gun II. Not knowing what it did, I didn't bother with it at first, until I unlocked the standard Injection Gun. Now, I've noticed the GJ (Good Job) hints at loading screens, telling me that firing upon my teammates with the Injection Gun is a good thing to do, but even after doing so, I really have no idea what it does. Can someone tell me what the effects of both weapons are on your teammates?

Also, I've noticed that the Injection Gun II seems to have two settings: Green, and Red. I'd appreciate it if these could be explained as well.

Each has two effects, depending on which mode you're in. I'd copy/paste them, but it's probably easier to just link the wiki page:

http://lostplanet.wikia.com/wiki/Injection_gun

Copied from that wiki:

The Injection Gun has two different fire modes, each with its own color and chosen by tapping the melee button. The selected fire mode is indicated by the colored circle in the "equipped weapon" indicator on your HUD and the shot color. The Injection Gun is a single shot weapon with great benefits. It's shots move moderately fast, straight, and far allowing the user to support their teammates at long range. Whether they're on foot or piloting a VS. The shots also have splash, which is very important and should be utilized. The user can effect themselves by shooting the floor or another point blank surface so the splash can hit them and if a team huddles around the user, all 4 players can be affected by 1 shot.

Red: The default shot increases the target's firepower by 300% for about 1 minute. Opposite effect on foes.

Blue: The alternate shot increases the defense of an ally by 300-400% for about 1 minute. Opposite effect on foes.

Happy hunting!