I don't know how the other feel about primary colors, but I'm definitely up for red with Karkat. You know how it's an important color for him, and he's taken some personal symbolism in it. (His token, a necklace with his sign on it, has a small red section where it was repaired after Shepard broke it off him in the "medieval" arena.) Like, it's blood: red blood. Humans have that! Unity with humans!! Holy shit wow.

Karkat's also going to be pushing a big unity with Panem and its people thing in his interview, very purposefully, so having that extra tie in would be good.

I like the idea of circles and rings, though - look, another thing his sign fits in! - and some kind of color contrasting too. Maybe if the primaries are an accent to black and white? I don't know what would look good, or what Trish would go for there.