Bug#1037960: The manpages of journalctl should explain bold (or semi-bold), yellow, and blue highlighting/emphasis

[Al Ma]

However, in the meantime, there has been an update of 
https://www.freedesktop.org/software/systemd/man/journalctl.html 
https://www.freedesktop.org/software/systemd/man/journalctl.html in this 
regard. The update does not fully resolve the issue but is better than nothing.