Pretty cool open-source software to colorize line-art automatically:
https://github.com/lllyasviel/style2paints
Example video: https://www.youtube.com/watch?v=Jtp6nUTjD6Y
I guess that could be useful when working on a open-source visual novel or maybe some simple cut scenes.
Edit: eh, the more recent releases are not (yet?) open-source :( And it sounds a bit like they are working on a commercial version.