Got into the game, and two of the players already had stuff painted up for Steiner and Davion, and a third player was leaning toward the idea of fielding a Kurita force. I decided to pick a suitable opponent, no matter who showed up, so I went with the Oberon Confederation, a former pirate group in the process of gradually becoming respectable, or at least less piratical. That lasted until the introduction of the Clans, at which point the Oberon Confederation simply ceased to exist, having been directly in the way of the advance. I eventually repainted a few of those 'Mechs.
My next option was to paint up a FWL force, which normally doesn't tangle with Davion or Kurita, but that can occasionally happen in the confused areas around Terra. It was either that or Liao, and one occasional player had a 'Mech in something that he felt qualified as Liao colors, plus I didn't care for the way they were being portrayed in the literature. Unfortunately, House Marik got pretty much ignored in most of the literature other than as a background character for everyone else's stories. Then the Jihad put an end to that, with them fragmenting into a bunch of squabbling mini-states for the next few decades (real time, as well as in the game timeline).
I ended up painting a bunch or 'Mechs in Outworlds Alliance colors, which again came to a sudden stop when Clan Snow Raven showed up and merged with them into some seriously FUBAR union of Machiavellian connivers with Amish-style pacifists.
Now I mostly just paint up stuff in generic camo colors (although I did do a couple of Clan 'Mechs in their respective Clan colors as OPFOR), and typically play Mercenary units. As said by a previous poster, the miniature is merely a token to represent the location and facing of the unit, and need not be exact, as long as both sides understand what it represents. This isn't Games Workshop, where the GW Police will show up at your house with guns drawn to confiscate your illegally painted miniature. Out of respect for other players, I try to at least use a miniature that either bears some vague resemblance to the unit being fielded, or that serves the same functional combat role, to make it easier to remember what it represents. I don't field a Stinger as a stand-in for an Atlas or a Marauder, since they don't look anything alike and are functionally completely different, but I might put a Catapult on the table to represent a Trebuchet if my Trebuchet miniature is already being used, despite the visual differences, because they're both "missile boats". A Vulture ("Mad Dog", for those of you who strayed onto the Clan Side) makes a reasonable proxy for a Marauder, if you don't have a Marauder (I do).
