I realize there are details in the show that probably bring this headcanon into question. But bear with me!
Combat Division
Invader Class (Red) - Trained in covert ops, Invaders are tasked with going undercover to enemy planets and blending in with the native life in order to prepare it for conquest by the Irken Armada.
Military Class (Black) - The Irkens programmed for the military make up the majority of the Irken Armada. They are trained to be the soldiers on the front line in battle, whether on land or through the stars.
Weapons Class (Yellow) - Battle seems to be a hobby to the Irken race. And working in close correspondence with the Innovations Class, the Weapons Class specializes in the building and development of the technology of Irken military offense. If the Military Class uses it in battle, the Weapons Class built it. Research & Analysis Division
Life Sciences Class (Green) - Pretty much every class depends on research. The Life Sciences Class specialize in all non-mechanical factors of Irken life, including biology, systematics, and agriculture.
Physical Sciences Class (Teal) - Irkens of the Physical Sciences Class are the ones that crunch the numbers of life and the math of how things work. Their specialties include the studies of space, sound, motion, and best of all - quantum physics.
Explorer Class (Purple) - Those Irkens programmed into the Explorer Class actually don’t see Irk much after initial training. Their job is braving the frontiers of space, mapping and scoping out the far reaches of the universe and reporting their findings to the Tallest. Engineering Division
Medical Class (White) - Seeing as how the PAK is the Irken life force, highly-trained medical technicians are needed to maintain and repair them. They work in close correspondence with the Life Sciences Class, but those in the Medical Class truly know the ins, outs, and facets of of the PAK and how it works - and is, in fact, the primary class in the production of every new PAK.
Innovations Class (Orange) - Those in the Innovations Class are essentially the inventors and artists of the Irken race. They design and build everything from cruisers to robo-technics to the structure capsules used by Invaders to establish their secret bases.
Communications Class (Blue) - The Communications Class is - aptly - the team behind every visual and aural form of communication used by the Irken Empire. Not only do they build the equipment, but also operate the Communications Center on both Irk and the Massive alike.—
When a smeet hatches, they are given a PAK designated to a random class, or whatever class is in demand. Each class is represented by a color, and each PAK is specialized to the tools and information needed for that class. There have been many instances through the Empire’s history where an Irken has transferred to a different class from which he/she was born into, but the PAK is still a way of designating what kind of tools and info he/she possesses. In order to become an Elite, an Irken must show superior knowledge and mastery in not only his/her class, but also the other classes of his/her division. For example: when Tallest Red and Purple were Elites, Red was a Combat Elite and Purple was a Research & Analysis Elite.
