|Founding||Originally a part of Rogue Trader's
|Successors of||Ultramarines. Maybe. Depends on who you ask.|
|Specialty||Eternally forgotten by their parents, dressing up as space Aztecs, being cryptically referenced again, being Gay, maybe doing a lot of spook and protesting against pollution and shit.|
|Colours||All the colors of the Rainbow (No durr...), but mainly Blue|
Back when Warhammer 40,000 was still called Rogue Trader, all of the First Founding Space Marine Chapters were known, and the Rainbow Warriors were one of them. Nothing else was known of them, except for the fact that the Sisters of Battle curb-stomped them at one point.
So apparently Games Workshop didn't think too highly of these guys, and in a Third Edition White Dwarf article, they were declared to be of a "later founding." They also hold the title of silliest space marine chapter name of all time, resembling that of a deranged LSD-dealing hippie cult that prowls the parking lots of Grateful Dead concerts with mangy dogs and backpacks full of spook, warp dust and flects. These degenerates existed at the time that GW came out with Rogue Trader (and still do, in parking lots wherever hippie music is played) but it is highly unlikely that they were any influence as they and similar organizations don't really have any reach in the UK (or anywhere outside the US, for that matter.)
They are also (and more probably) directly named after a radical environmentalist ship that got sunk by the
frogs French for nosing around their weapons of mass destruction, which was in the news and highly controversial around the time when Rogue Trader was published. So take your pick, this chapter's theme is apparently either drug dealing or eco-terrorism. Edgier than they sound.
In the 5th Edition Space Marines Codex, the planet "Prism" is designated as the homeworld of "<<record deleted>>," a chapter which bears the Rainbow Warriors' insignia. Prism has been found! Get the 6th edition and look in the Northwestern border of the Vidar Sector located in the Imperius Dominatus. So apparently one of the lost Chapters might have been exterminus extremis due to being filthy hippies. Good to know.
Sadly, this fun fan theory is dead on arrival due to the retcon in which ye olde Rainbow Warriors were relegated to an unspecified "later founding," nonetheless, one imagines that the Emperor's reaction, not to mention that of the Inquisition or Black Templars, to either species of hippie, drug-dealing or boat-sinking, and that it certainly wouldn't be too friendly. More canonically, though, it's noted that the image for Sisters of Battle in the Rogue Trader rulebook has a Sister shoot down what appears to be a Rainbow Warrior. Such a square harshing the guy's mellow. This combined with the <<record deleted>> statement above suggest they were filthy
hippies heretics who got purged.
Also, to add to the eclectic weirdness and confused aesthetic of the whole chapter, somewhere along the way, people thought it would be cool to envision the Rainbow Warriors as Aztec Marines. There's also a basically-the-Rainbow-Warriors chapter called the Death Strike, which, simply as a name, is hilariously edgy for the opposite reasons that the Rainbow Warriors themselves are edgy. Apparently, they have a huge hate-on for the Ultramarines (not unlike some folks we know) for helping to excommunicate their brother chapter. HMM.
They're still even kicking around in the grim darkness of the 41st Millennium if the 6th Edition Codex is anything to go by. They, the Relictors and the Fire Lords fought a bloody powerful Demonic incursion, but ended up losing a fair chunk of their chapter, including their Chapter Master. Whether they'll eventually get NOM'd by the 'nids like other very 985.M2-era material that hasn't aged too well remains to be seen, as does whether or not anyone really cares. General fanon holds they are Lost Legion Loyalists brainwashed into believing they are Ultramarines, supported by mentions that Ultramarines got a large number and supply boost when the lost were, well, lost.
According to the short Story "War in the Meuseum", the Rainbow Warriors are confirmed to be an exhibit in our favorite curator's collection, Trazyn the Infinite.