--- a/browser/components/extensions/test/browser/browser.ini
+++ b/browser/components/extensions/test/browser/browser.ini
@@ -306,9 +306,8 @@ tags = fullscreen
 [browser_ext_windows_size.js]
 skip-if = os == 'mac' || (debug && os == "linux" && os_version == "18.04") # Fails when windows are randomly opened in fullscreen mode, Bug 1638027
 [browser_ext_windows_update.js]
 skip-if = (verify && (os == 'mac')) || (os == 'linux' && bits == 64 && os_version == '18.04')  # Bug 1533982 for linux1804
 tags = fullscreen
 [browser_ext_contentscript_animate.js]
 [browser_ext_contentscript_cross_docGroup_adoption.js]
 [browser_ext_contentscript_cross_docGroup_adoption_xhr.js]
-[browser_toolbar_prefers_color_scheme.js]

deleted file mode 100644
--- a/browser/components/extensions/test/browser/browser_toolbar_prefers_color_scheme.js
+++ /dev/null
@@ -1,51 +0,0 @@
-/* Any copyright is dedicated to the Public Domain.
-   http://creativecommons.org/publicdomain/zero/1.0/ */
-
-"use strict";
-
-add_task(async function testThemeDeterminesToolbarQuery() {
-  let darkModeQuery = window.matchMedia("(prefers-color-scheme: dark)");
-  let darkToolbarQuery = window.matchMedia(
-    "(-moz-toolbar-prefers-color-scheme: dark)"
-  );
-
-  let initialDarkModeMatches = darkModeQuery.matches;
-
-  let darkExtension = ExtensionTestUtils.loadExtension({
-    manifest: {
-      theme: {
-        colors: {
-          toolbar: "rgba(12, 12, 12, 1)",
-        },
-      },
-    },
-  });
-  let lightExtension = ExtensionTestUtils.loadExtension({
-    manifest: {
-      theme: {
-        colors: {
-          toolbar: "rgba(255, 255, 255, 1)",
-        },
-      },
-    },
-  });
-
-  await Promise.all([
-    TestUtils.topicObserved("lightweight-theme-styling-update"),
-    darkExtension.startup(),
-  ]);
-
-  is(darkModeQuery.matches, initialDarkModeMatches, "OS dark mode unchanged");
-  ok(darkToolbarQuery.matches, "toolbar query is dark mode");
-
-  await Promise.all([
-    TestUtils.topicObserved("lightweight-theme-styling-update"),
-    lightExtension.startup(),
-  ]);
-
-  is(darkModeQuery.matches, initialDarkModeMatches, "OS dark mode unchanged");
-  ok(!darkToolbarQuery.matches, "toolbar query is light mode");
-
-  await lightExtension.unload();
-  await darkExtension.unload();
-});

--- a/browser/modules/ThemeVariableMap.jsm
+++ b/browser/modules/ThemeVariableMap.jsm
@@ -1,16 +1,14 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 var EXPORTED_SYMBOLS = ["ThemeVariableMap", "ThemeContentPropertyList"];
 
-const { Services } = ChromeUtils.import("resource://gre/modules/Services.jsm");
-
 const ThemeVariableMap = [
   [
     "--lwt-accent-color-inactive",
     {
       lwtProperty: "accentcolorInactive",
     },
   ],
   [
@@ -52,32 +50,16 @@ const ThemeVariableMap = [
     {
       lwtProperty: "tab_background_separator",
     },
   ],
   [
     "--toolbar-bgcolor",
     {
       lwtProperty: "toolbarColor",
-      processColor(rgbaChannels, element) {
-        if (!rgbaChannels) {
-          Services.prefs.setBoolPref(
-            "browser.theme.dark-toolbar-theme",
-            element.ownerGlobal.matchMedia("(prefers-color-scheme: dark)")
-              .matches
-          );
-          return null;
-        }
-        const { r, g, b, a } = rgbaChannels;
-        Services.prefs.setBoolPref(
-          "browser.theme.dark-toolbar-theme",
-          _isColorDark(r, g, b)
-        );
-        return `rgba(${r}, ${g}, ${b}, ${a})`;
-      },
     },
   ],
   [
     "--toolbar-color",
     {
       lwtProperty: "toolbar_text",
     },
   ],
@@ -196,13 +178,8 @@ const ThemeVariableMap = [
 const ThemeContentPropertyList = [
   "ntp_background",
   "ntp_text",
   "sidebar",
   "sidebar_highlight",
   "sidebar_highlight_text",
   "sidebar_text",
 ];
-
-// This is copied from LightweightThemeConsumer.jsm.
-function _isColorDark(r, g, b) {
-  return 0.2125 * r + 0.7154 * g + 0.0721 * b <= 110;
-}

--- a/layout/style/test/chrome/chrome-only-media-queries.js
+++ b/layout/style/test/chrome/chrome-only-media-queries.js
@@ -34,11 +34,9 @@ const CHROME_ONLY_TOGGLES = [
 ];
 
 // Non-parseable queries can be tested directly in
 // `test_chrome_only_media_queries.html`.
 const CHROME_ONLY_QUERIES = [
   "(-moz-os-version: windows-win7)",
   "(-moz-os-version: windows-win8)",
   "(-moz-os-version: windows-win10)",
-  "(-moz-toolbar-prefers-color-scheme: dark)",
-  "(-moz-toolbar-prefers-color-scheme: light)",
 ];

--- a/modules/libpref/init/StaticPrefList.yaml
+++ b/modules/libpref/init/StaticPrefList.yaml
@@ -1139,24 +1139,16 @@
   mirror: always
 
 # Force usage of in-memory (rather than file on disk) media cache for video streaming when private browsing
 - name: browser.privatebrowsing.forceMediaMemoryCache
   type: bool
   value: false
   mirror: always
 
-# Whether the toolbar is dark/light/auto.
-# Controls @media -moz-toolbar-prefers-color-scheme.
-- name: browser.theme.dark-toolbar-theme
-  type: RelaxedAtomicBool
-  value: false
-  mirror: always
-  rust: true
-
 # Enable Proton restyle. Requires restart.
 - name: browser.proton.enabled
   type: RelaxedAtomicBool
   value: true
   mirror: always
   rust: true
 
 - name: browser.proton.contextmenus.enabled

--- a/servo/components/style/gecko/media_features.rs
+++ b/servo/components/style/gecko/media_features.rs
@@ -401,31 +401,16 @@ fn eval_prefers_color_scheme(device: &De
     let prefers_color_scheme =
         unsafe { bindings::Gecko_MediaFeatures_PrefersColorScheme(device.document()) };
     match query_value {
         Some(v) => prefers_color_scheme == v,
         None => true,
     }
 }
 
-/// The color-scheme of the toolbar in the current Firefox theme. This is based
-/// on a pref managed by the front-end.
-fn eval_toolbar_prefers_color_scheme(_: &Device, query_value: Option<PrefersColorScheme>) -> bool {
-    let prefers_color_scheme = if static_prefs::pref!("browser.theme.dark-toolbar-theme") {
-        PrefersColorScheme::Dark
-    } else {
-        PrefersColorScheme::Light
-    };
-
-    match query_value {
-        Some(v) => prefers_color_scheme == v,
-        None => true,
-    }
-}
-
 bitflags! {
     /// https://drafts.csswg.org/mediaqueries-4/#mf-interaction
     struct PointerCapabilities: u8 {
         const COARSE = structs::PointerCapabilities_Coarse;
         const FINE = structs::PointerCapabilities_Fine;
         const HOVER = structs::PointerCapabilities_Hover;
     }
 }
@@ -634,17 +619,17 @@ macro_rules! bool_pref_feature {
     }};
 }
 
 /// Adding new media features requires (1) adding the new feature to this
 /// array, with appropriate entries (and potentially any new code needed
 /// to support new types in these entries and (2) ensuring that either
 /// nsPresContext::MediaFeatureValuesChanged is called when the value that
 /// would be returned by the evaluator function could change.
-pub static MEDIA_FEATURES: [MediaFeatureDescription; 62] = [
+pub static MEDIA_FEATURES: [MediaFeatureDescription; 61] = [
     feature!(
         atom!("width"),
         AllowsRanges::Yes,
         Evaluator::Length(eval_width),
         ParsingRequirements::empty(),
     ),
     feature!(
         atom!("height"),
@@ -844,22 +829,16 @@ pub static MEDIA_FEATURES: [MediaFeature
         ParsingRequirements::CHROME_AND_UA_ONLY,
     ),
     feature!(
         atom!("-moz-non-native-content-theme"),
         AllowsRanges::No,
         Evaluator::BoolInteger(eval_moz_non_native_content_theme),
         ParsingRequirements::CHROME_AND_UA_ONLY,
     ),
-    feature!(
-        atom!("-moz-toolbar-prefers-color-scheme"),
-        AllowsRanges::No,
-        keyword_evaluator!(eval_toolbar_prefers_color_scheme, PrefersColorScheme),
-        ParsingRequirements::CHROME_AND_UA_ONLY,
-    ),
 
     lnf_int_feature!(atom!("-moz-scrollbar-start-backward"), ScrollArrowStyle, get_scrollbar_start_backward),
     lnf_int_feature!(atom!("-moz-scrollbar-start-forward"), ScrollArrowStyle, get_scrollbar_start_forward),
     lnf_int_feature!(atom!("-moz-scrollbar-end-backward"), ScrollArrowStyle, get_scrollbar_end_backward),
     lnf_int_feature!(atom!("-moz-scrollbar-end-forward"), ScrollArrowStyle, get_scrollbar_end_forward),
     lnf_int_feature!(atom!("-moz-scrollbar-thumb-proportional"), ScrollSliderStyle),
     lnf_int_feature!(atom!("-moz-overlay-scrollbars"), UseOverlayScrollbars),
     lnf_int_feature!(atom!("-moz-menubar-drag"), MenuBarDrag),

--- a/toolkit/modules/LightweightThemeConsumer.jsm
+++ b/toolkit/modules/LightweightThemeConsumer.jsm
@@ -473,12 +473,11 @@ function _rgbaToString(parsedColor) {
   }
   let { r, g, b, a } = parsedColor;
   if (a == 1) {
     return `rgb(${r}, ${g}, ${b})`;
   }
   return `rgba(${r}, ${g}, ${b}, ${a})`;
 }
 
-// There is a second copy of this in ThemeVariableMap.jsm.
 function _isColorDark(r, g, b) {
   return 0.2125 * r + 0.7154 * g + 0.0721 * b <= 110;
 }

--- a/widget/nsXPLookAndFeel.cpp
+++ b/widget/nsXPLookAndFeel.cpp
@@ -417,17 +417,16 @@ void nsXPLookAndFeel::OnPrefChanged(cons
 }
 
 static constexpr nsLiteralCString kBoolMediaQueryPrefs[] = {
     "browser.proton.enabled"_ns,
     "browser.proton.contextmenus.enabled"_ns,
     "browser.proton.modals.enabled"_ns,
     "browser.proton.doorhangers.enabled"_ns,
     "browser.proton.places-tooltip.enabled"_ns,
-    "browser.theme.dark-toolbar-theme"_ns,
 };
 
 // Read values from the user's preferences.
 // This is done once at startup, but since the user's preferences
 // haven't actually been read yet at that time, we also have to
 // set a callback to inform us of changes to each pref.
 void nsXPLookAndFeel::Init() {
   MOZ_RELEASE_ASSERT(NS_IsMainThread());

--- a/xpcom/ds/StaticAtoms.py
+++ b/xpcom/ds/StaticAtoms.py
@@ -2218,17 +2218,16 @@ STATIC_ATOMS = [
     Atom("_moz_gtk_csd_maximize_button", "-moz-gtk-csd-maximize-button"),
     Atom("_moz_gtk_csd_close_button", "-moz-gtk-csd-close-button"),
     Atom("_moz_gtk_csd_reversed_placement", "-moz-gtk-csd-reversed-placement"),
     Atom("_moz_proton", "-moz-proton"),
     Atom("_moz_proton_contextmenus", "-moz-proton-contextmenus"),
     Atom("_moz_proton_doorhangers", "-moz-proton-doorhangers"),
     Atom("_moz_proton_modals", "-moz-proton-modals"),
     Atom("_moz_proton_places_tooltip", "-moz-proton-places-tooltip"),
-    Atom("_moz_toolbar_prefers_color_scheme", "-moz-toolbar-prefers-color-scheme"),
     Atom("_moz_system_dark_theme", "-moz-system-dark-theme"),
     # application commands
     Atom("Back", "Back"),
     Atom("Forward", "Forward"),
     Atom("Reload", "Reload"),
     Atom("Stop", "Stop"),
     Atom("Search", "Search"),
     Atom("Bookmarks", "Bookmarks"),