Been playing a bit with SketchUp's colours...
For some reason I imagine the Legion's basic colour scheme to be grey, the blue is just a very...well, trendy futuristic colour I guess!
I'm imagining the basic game/battles to be some form of internal strife, it's the Legion fighting itself. I would imagine this strife, or at least the main campaign/storyline for the space ship game to be along the lines of either a colonial war or a war between equalized powers.
The colonial war would be very much like the wars of independence throughout the Americas. The colonies didn't really seek independence because they wanted everybody to live in freedom (Haiti probably being the big exception), their resistance has been very economic/political in nature, especially in Latin America, meaning they wanted to get more power and profit, not longer interested in sending it off to the distant throne in the old continent. In case of the Legion these would be more 'distant' colonies (subsidiary worlds) that seen great autonomy, forming their own alliances. Of course the Legion as whole isn't so happy about this idea and starts sending in their fleet to teach these secessionists a lesson.
The war between 'equal powers' would be akin to two colonial powers fighting amongst themselves for domination. Kinda like the British versus the French I guess. Perhaps some sort of 'small Psidemic' occurred, leaving vast parts of the Legion empire separated, it basically cut the empire in two factions, both believing themselves to be the true Legion. They try to establish new colonies and outdo the other one. It could also be more of a Cold War scenario in which both these factions try to fight a proxy war, akin to the Soviets and Americans. But then with elements of the French/British wars (got to love naval war).
All very possible scenarios of course. I would imagine that symbolically these factions be white (pearl) and black (obsidian), each a different aspect of the Legion, together being Legion grey. Oh well...food for thought!