highlight.js 11.0 was recently released with numerous improvements but also some breaking changes.
From my point of view, the old github theme integrates nicely with the SWH color theme while the updated one does not, see below:
Hopefull we can restore the old theme after highlight.js upgrade using a dedicated CSS file.
I also noticed a regression regarding Python highlighting in highlight.js 11.0, I have submitted a fix that will be integrated in the next release of the library.
So no need to rush for that upgrade at the moment as it is an important part of the Web UI and needs more testing before a deployment.