Yes that seems to be my problem (specifically part 2 of that).

I think this is re-occuring right now on Solus 4.1

I have been able to switch back to Plata-Noir-Compact after editing the file you pointed out (~/.Texworks/configuration/syntax-patterns.txt) to use lighter colous. (Basically I replaced darkred with salmon, darkblue with dodgerblue and darkgreen with green).

Do you by any chance have a link to the source code where you checked? I will try to raise an issue in TeXworks for this so would like to provide as much context as possible.

I've installed various themes by searching for "gtk-theme" in the software center.