Bugzilla

In forced colors mode, Firefox inconsistently mixes colors from the current Firefox theme and the forced colors palette supplied by Windows. This inconsistent application of colors leads to a wide variety of bugs. Note that these bugs only affect Windows users: Mac and Linux accessibility settings offer increased contrast, but not forced colors.

The profiles team encountered many contrast bugs caused by the mix of profiles theme colors and forced colors in the browser UI. After discussion with experts from the add-ons, accessibility, and DOM teams, we plan to resolve this class of bugs for Firefox as follows:
* disable theme colors in forced-colors mode
* add a "themes disabled" warning message to the about:addons page, and show it when in forced-colors mode
* put both changes behind a pref so we can revert the behavior if something breaks in release

We considered whether we might break Firefox for forced-colors users who use Firefox themes, but telemetry data[1] shows that most forced-colors users have the default theme. So, we expect that these changes will improve Firefox accessibility for most forced-colors users.

[1] (https://sql.telemetry.mozilla.org/queries/110393#271010)

In forced colors mode, Firefox inconsistently mixes colors from the current Firefox theme and the forced colors palette supplied by Windows. This inconsistent application of colors leads to a wide variety of bugs. Note that these bugs only affect Windows users: Mac and Linux accessibility settings offer increased contrast, but not forced colors.

The profiles team encountered many contrast bugs caused by the mix of profiles theme colors and forced colors in the browser UI. After discussion[1] with experts from the add-ons, accessibility, and DOM teams, we plan to resolve this class of bugs for Firefox as follows:
* disable theme colors in forced-colors mode
* add a "themes disabled" warning message to the about:addons page, and show it when in forced-colors mode
* put both changes behind a pref so we can revert the behavior if something breaks in release

We considered whether we might break Firefox for forced-colors users who use Firefox themes, but telemetry data[2] shows that most forced-colors users have the default theme. So, we expect that these changes will improve Firefox accessibility for most forced-colors users.

[1] https://docs.google.com/document/d/1vonoQnVsJWbbU0QbUAuctyRPr7RxI6uxjieiH5WS14o/edit?tab=t.0 (note 9/15/25: working on making this document world-readable)
[2] (https://sql.telemetry.mozilla.org/queries/110393#271010)