Ah, I just had a brainwave and remembered the name. I was thinking of *[Iron**born][1]**,* by Olle Lindestad (who it looks like is currently working on another webcomic, "Current Culture"). The blurb:

> Robots aren't supposed to be able to use magic. But Opal is, and she's as confused about it as anyone. As conflict looms between a city of magic and a city of robots, she'll have to be quick on her feet...

It apparently was "published online between 2007 and 2014"; the original website is no longer up (so I'm not sure if my memory of its having a red color scheme is correct, although the logo is red) but part of it is currently online at a different website. The last page uploaded so far is [page 160][2], from 2010. But the author made a [blog post on November 6, 2017][3] indicating that more pages may be uploaded at some point in the future.


  [1]: http://ollelindestad.com/ironborn
  [2]: http://ollelindestad.com/ironborn-archive/2018/2/28/ironborn-page-160
  [3]: http://ollelindestad.com/the-haps/2017/11/6/mysterious-alien-flash-drives