Does it still happen in Troubleshoot Mode?

Do you see text if you try to select text or use select all in a place where you expect text in case text color and background color are the same?

Did you make changes to the default colors from back text on light background?

• Settings -> General -> Language and Appearance -> Colors

Trouble shooting mode didn't help & it is not a colour issue. The attached screenshots from CNN illustrate the problem. The first "Ghost guns" article, which is reached via a link from the main body of the CNN site, using TOR, is fine. The second one shows random links around the page where there should be readable text.

What font(s) is Firefox using for various parts of the page?

You can right-click and select "Inspect" to open the built-in Inspector with this element selected.

• https://firefox-source-docs.mozilla.org/devtools-user/page_inspector/how_to/open_the_inspector/
• https://firefox-source-docs.mozilla.org/devtools-user/page_inspector/how_to/examine_and_edit_html/

You can check in the Rules tab in the right panel in the Inspector what font-family is used for selected text. You can check in the Fonts tab in the right panel in the Inspector what font is actually used because Firefox might be using a different font than specified by the website. If the Fonts tab is hidden, click the Down arrow at the right end.

• https://firefox-source-docs.mozilla.org/devtools-user/page_inspector/how_to/edit_fonts/

You can check in Font Book for font issues like corrupted and duplicate fonts. You may find that this can be resolved by finding and removing duplicate fonts installed in the local ~/Library/Fonts folder, that are conflicting with standard system fonts.

Note that you should be careful about disabling "Allow pages to choose their own fonts, instead of your selections above" as this will cause issues with iconic fonts used by webpages to display small icons (you may see text labels instead of icons).