Really, I should have filed this under Nightly's bug tracker...

What theme do you use to get this blue color ? Are you using userChrome.css or userContent.css?

Did you try Troubleshoot Mode? Did you check this in a new, clean, profile (always the first to check in case of issues with Nightly) ?

You can try the daily threads on the mozillaZine Builds forum.

What theme do you use to get this blue color ? Are you using userChrome.css or userContent.css?

None. What theme could apply an alternating image (with hash and diagonal lines), only in 3 tabs of Page Info?

It still occurs in troubleshooting mode, as would be expected. Nightly has broken Page Info before, and eventually fixed it. I made this thread just to bring it to their attention, although I imagine others users have noticed.

I made a mistake. It's also in General.

It occurs with a new profile, as well, as I expected.

Thank you for helping to test Firefox Nightly. I recommend that you file a bug report so that our developers can look into this further. See File a bug report or feature request for Mozilla products for details.

I still don't know/see where the blue color comes from. Do you have a Windows theme that styles content with this background color ?

I see code for treechildren with a treechildren::-moz-tree-row(multicol, odd) {} selector.

• https://searchfox.org/mozilla-central/search?q=%3A%3A-moz-tree-row&path=

You can check this in the Browser Toolbox (pageInfo.xhtml).

• https://firefox-source-docs.mozilla.org/devtools-user/browser_toolbox/

Does it still happen in a new profile (without signing into sync account)?

These colors usually come from your system theme. Have you ever applied any Windows theme customizations, installed any theme software or registry modifications?

2023-12-29-09-25-37 build fixed it. I tested 2023-12-28-04-12-17, with a new profile, and the bug is still there. So, thank you to whomever fixed it.