so I’m about a third of the way through clash of kings and there’s been no mention whatsoever of renly being gay
is this just a thing in the show or…?
No, he’s gay in the books, but it’s more subtextual since both Renly and Loras are not POV characters and they’re closeted. GRRM has confirmed several times that Renly/Loras was definitely a thing in the books, we weren’t imagining it.
They seemed like a couple to me in ACoK, but I know many were surprised by Renly’s gayness on the show. For what it’s worth, I thought it was super obvious in the books by A Storm of Swords, based off a comment Loras made to Jaime, and a very crude remark Jaime makes about Loras, Renly and swords.
Actually here’s a good website post that outlines the examples of when their gayness is referred to.
(The Rainbow Guard reference is just a coincidence though, according to GRRM. He says he had no idea that rainbows had anything to do with LGBT stuff. Seriously.)