Because it´s so piss-easy to alter these things once the template is done, here´s an example of how a Csye Unit might place its markings.

There are no rules where and how to place the markings, for the whole of the Csye realm, and pretty much every System does it as they please. There are just a few things that will always be identical in -all- Csye Units, as a matter of tradition.

Red always denotes Space-borne Marines. They are an extremely specialised branch, and should not be compared to, say, the USMC (because that´s probably the real-world service that comes to mind first when thinking of "Marines"). The SbM Units have only one purpose: ship-to-ship boarding operations.
This is probably the single-most deadly business a soldier can get into. They have the highest casualty rate, simply because usually getting to your target is a hit and miss affair. In this Universe, there aren´t such things as transporters á la Star Trek: the only way to get to a ship is to physically latch onto it.

The velocities involved in this are tremendous - Spaceships move at velocities in the thousands of kilometers per hour, and boarding vehicles have to somehow track, close and attach to their target without missing it, without getting shot down, and without destroying it. At speeds where a 3 kg heavy steel ball can destroy a cruiser sized vessel, slamming into it with a 25 ton assault boat will only leave a rapidly expanding cloud of dust and shrapnel.

Once they actually are INSIDE their target, however, these Warriors really come into their own. Trained in Zero-G combat, Hand-to-Hand fighting and usually equipped with very bulky and heavy armour and soft-kill weapons, they are able to defeat even battleship sized vessels in short order, with team sizes of 8 members.

Inside Ships, hard-kill weapons, such as Battle rifles, Grenades and other stuff that is designed to explosively tear things apart cannot be used: this is why the SbM use the heaviest armour that can physically be carried inside a spaceship: the only weapons that can effectively used against them with any sort of lethal effect are close combat weapons.
Due to their extensive training, no common spacefarer has a realistic chance of actually defeating such a soldier in zero-g hand to hand combat. The sheer weight of their armour in motion is enough to grind limbs into paste, and crush ribs as if they were rotten twigs.

The markings are those of Priory 15, of the Gora-El system Home Defense. The indicator below the Unit marking tells that this Warrior belongs to 1st Company (Square Marking), 2nd Platoon (2 verical bars), Platoon Command Element (Stripe on both chest and shoulder pad).