Examples/Try it inherits the font color from browser prefs

Summary

If user changes font color in the browser settings, the text in the examples will also change it, but the background will remain white. This can cause contrast issues.

URL

Any page with Examples section, e.g:
https://developer.mozilla.org/en-US/docs/Web/HTML/Element/a#examples
https://developer.mozilla.org/en-US/docs/Web/HTML/Element/meter#examples

Reproduction steps

1. Go to about:config,
2. Change the value of;
   • browser.anchor_color to #ff0000,
   • browser.visited_color to #00ff00,
   • browser.display.foreground_color to #ffffff,
   • browser.display.background_color to #000000,
3. Go to;
   • https://developer.mozilla.org/en-US/docs/Web/HTML/Element/a#examples,
   • https://developer.mozilla.org/en-US/docs/Web/HTML/Element/meter#examples,
4. See red/lime links and white text on white background.

Expected behavior

Links and text shouldn't change color based on these prefs.

Actual behavior

Links and text change color depending on these prefs.

Device

Desktop

Browser

Firefox

Browser version

Pre-release (e.g. Beta, Nightly or Canary)

Operating system

Linux

Screenshot

Example video with browser.anchor_color. From the first URL.

https://user-images.githubusercontent.com/87250374/165396032-5c76e841-ee8a-427f-a145-6e16229eace4.mp4

Example screenshot with browser.display.foreground_color = #ffffff. Only the selected part of the text is visible. From the second URL.

Anything else?

The Try it boxes have a similar problem only with links. Should this be a new bug report?

Validations

• I have read the Community Participation Guidelines.
• I have verified that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• I have checked that this is a concrete bug. For Q&A open a GitHub Discussion.

Reproduce the issue on the Examples pages for the HTML a and meter elements using the listed Firefox about:config color preferences. Start by tracing the Examples and Try it sections in the frontend; done means their text and links retain readable colors instead of inheriting browser preferences, with the reported contrast issue no longer visible.