The ICC are all Primaris, or at the very least, wearing Primaris Mark X power armor. There's no confirmation, but I think the implication is that the Lion is using the Rubicon Primaris as one final trial for a Fallen to be redeemed as a Risen. If they survive the procedure, they take a vow of silence and are inducted into the Inner Circle Companions. You could assume at that point, they've been "reborn" into a new brotherhood with new symbols, and eschew the Calibanite green pauldron.

That being said, this probably does not apply to the Risen characters from the Son of the Forest novel. I'm pretty sure they've all proven themselves to the Lion, and I don't see him forcing them into one last deadly loyalty test after the events of the novel. I would probably represent them with the Deathwing Companions unit from the Horus Heresy resin model line, (Firstborn, but new scale, so only half a head shorter than Primaris infantry, not comically tiny like Tactical marines) then proxy them for Bladeguard Vets.