What? I've seen lots of tubes that may or may not have been clear, I really don't know, emitting light blue glows. Like, I used to go into Spencer's at the local mall a couple decades ago... I would have no clue what the difference is here.

They're made of a distinctively clear quartz glass (used because regular glass is quite effective at blocking UVC), and you can see the filaments at the ends. Hopefully you won't have to ever experience looking at a lit UVC tube, but they appear very different from regular fluorescents.

The comment here has a link to a previous incident of this happening, which shows what UVC tubes look like: https://news.ycombinator.com/item?id=38170902

Well, good to know! Thanks! But this would not have previously been obvious to me at all.

Here' a video on this incident, demonstrating the differences between the different tubes and showing what to look for: https://www.youtube.com/watch?v=6DlfLthx89E