[ownedbycats]

I'm not sure how applicable this is to everything else, but JimmXinu modified FFF several months ago to make the syntax highlighting more readable:
https://github.com/JimmXinu/FanFicFa...highlighter.py

This looks to be the relevant part

        try:
            if QApplication.instance().is_dark_theme:
                colors = {
                    'knownentries':Qt.green,
                    'errors':Qt.red,
                    'allkeywords':Qt.magenta,
                    'knownkeywords':QColor(Qt.blue).lighter(150),
                    'knownsections':Qt.darkCyan,
                    'teststories':Qt.cyan,
                    'storyUrls':Qt.magenta,
                    'comments':Qt.yellow
                    }
        except Exception as e:
            logger.error("Failed to set dark theme highlight colors: %s"%e)