User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:109.0) Gecko/20100101 Firefox/115.0

Steps to reproduce:

Two scenarios - A) on Mastodon, simply look at a user profile, and the "Follows You" icon above the avatar is shown as black text on a very dark grey background, while it's black on white for other browsers or other users with Firefox.
B) on Google Maps, various icons are shown as colour-hashed squares. Easy example is highway numbers are all striped-boxes. In a city, select 'Hotels' and the screen is a mess of overlapping striped boxes.
Using MacOSX 11.7.8 (Big Sur) with Firefox 115 on a MacBookPro

I'm speculating that these are both related to something messing up style settings.

Actual results:

Visit one of those websites, and I see the bad styling results. I've turned off all extensions and add-ons, and restarted firefox, but there's no improvement. Changed theme from light to auto theme with no improvement.

Added a screenshot of the hotels situation on GoogleMaps - looks like I can only attach one prob example image to this form.

Expected results:

I should see black-text on white background for the Mastodon UI example and should see proper highway numbers and icons in Google Maps

The Bugbug bot thinks this bug should belong to the 'Firefox::Theme' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

Update - it's been discovered that the about:config setting for resistFingerprinting is the culprit for the highway numbers and hotels bug. With the resistFingerprinting turned to "false" the 'B' problem goes away.

The 'A' problem though remains. Black text against an almost-black background, while other browsers show it as black on white, and many other firefox users see black on white too.

Tried turning Theme to "System Theme - auto" instead of previous "light" and problem remains.

The follows you text seems correct when I tested locally. Did you try in a fresh profile?

Updating bug to track just the Mastodon issue, as the other is somewhat expected with resistFingerprinting enabled.

Ross - a URL showing the Mastodon issue would be useful; as there isn't a single Mastodon instance different servers are likely to have different html/css/js (fun fact - there's currently 11,226 Mastodon instances).

The "follows you" tag and various brief pop-up "message posted" fields that were black on dark grey were on the most popular mastodon.social instance of Mastodon.

But while the problem had persisted for me for several weeks (and was consistent for my profile on two different macbooks) it went away yesterday. I suspect there was a change in the mastodon 4.1 nightlies.

Just for further background, here is a post from July9 with a screen shot of the text colouring issue:
https://mastodon.social/@ottaross/110684926724244475
Response comments from others indicated they didn't have the same issue on their various instances and profiles.

Anyway, the problem has resolved itself. Thx for anyone who looked into it.