The black collar is... bad. Castiel dislikes wearing it because it stands for everything their relationship usually isn't about. The blue collar is a sign of belonging, something he picked himself and had Sam fasten onto him.

He'd sucked Sam off in the dressing cabin, fully aware that all the privacy they had was owned to a few rows of shelves and the music blasting in the store.

The black punishment collar had been a later purchase, and it rarely ever came into use. Castiel raises his chin, though not his eyes, refusing to meet Sam's. They are not equals tonight. Not in the way they usually are in this arrangement. Tonight, Sam calls the shots, and Castiel will do nothing but receive the punishment his dominant sees fit for him.

And oh, how he wants that.