I've been digging around for Rainbow Warriors fluff, since last year when the C:
SM came out. I like to follow Phillip Sibbering's Aztec theme. I think he's also the one who said they were an ultramarines succesor chapter. (I think he just made that up though, and its not
GW canon.)
My army is still, in the early stages though. Just two tactical squads complete. One day I will have a "Full spectrum" company. (Which will have 6
tac squads, and 1
dev squad each with a different coulour on their shoulder. plus some vets and termis to make it up to 100 Rainbow warriors!)
I like the idea that the inquisition has hunted them. But that's all cool now (according to Phillip S, Papa smurf didn't like to see a successor chapter get beats so he called up the =I= and got it all smoothed over

)
I don't get all the gay jokes though. seem a bit lame to me. I agree with the poster who pointed out that it may just happen when you've got 1000 hormone-filled beefed up guys, who train together all day long, miles from home, in space, HURR!