I'm on PC-NA, and just ran into a bug when I tried changing Sharp-as-Night's outfit. At first I tried dyeing the Austere Warden Outfit (yes, I have ESO+), but it kept reverting back to its original color once I'd exited the station. Switched to Black Hand Robe, and it alternates between the colors I chose and some grayish-brown hue that is not the outfit's original color, as shown in the screenshots.
The outfit chosen in the Collections part in Sharp's Companion menu alternates between having a check mark and the icon similar to when you hide a head or shoulders armor piece.
This happened for both outfits I tried dyeing.
l'm going to wait to spend more gold at the outfit station once his outfit is consistently staying a color I like. Hope this provides the info you need to address the issue, and please let me know if I need to provide any more details that I've left out. I understand that this isn't a game-breaking or pressing bug, though, and that it could take some time to get to.