pict attached.

Hmm, how did that happen? As a Windows user, I'm at a bit of a disadvantage sorting out Linux issues because different system themes may influence the colors, in addition to built-in settings. Does your system have a dark theme? Firefox's built-in pages can be restyled by creating a userContent.css file and adding custom style rules. If you don't get a suggestion from a Linux user here, you might try: https://www.reddit.com/r/FirefoxCSS/