For the barge, carrying or wearing his crown forces Yellow into cohabitation with whoever is in possession of it, if they choose to allow him that entry. Otherwise, they will be able to hear and speak to him while holding the crown. He has no choice one way or the other regarding this, but unlike John can't leave after possession occurs unless he is allowed to do so. In other words, if a warden sees him throwing a shitfit they can grab his crown and make him relax. Of course, this could become an issue if a fellow inmate decides to get handsy.

During possession, he'll gain access to one of the holder's senses at random/by player preference. He'll also be able to talk silently in the head of whoever has him in hand, but cannot speak out of his holder's mouth, read any of their thoughts, or actively control their actions. Certain supernatural senses and/or beings can hear him talking inside someone else's head even if the same senses couldn't just read someone's mind. (If some of this sounds familiar it's because I straight-up stole it from Danii's description of John's interactions and limitations. With permission!)