--- a/browser/themes/windows/browser-aero.css
+++ b/browser/themes/windows/browser-aero.css
@@ -50,24 +50,24 @@
   @media not all and (-moz-os-version: windows-win7) {
     @media not all and (-moz-os-version: windows-win8) {
       @media (-moz-windows-default-theme) {
         :root:not(:-moz-lwtheme) {
           background-color: hsl(0, 0%, 78%);
         }
 
 %ifdef MOZ_PHOTON_THEME
-        @media (-moz-windows-accent-color-applies: 0) {
+        @media (-moz-windows-accent-color-in-titlebar: 0) {
           :root[tabsintitlebar]:not(:-moz-lwtheme) {
             background-color: hsl(235,33%,19%);
             --titlebar-text-color: hsl(240,9%,98%);
           }
         }
 
-        @media (-moz-windows-accent-color-applies) {
+        @media (-moz-windows-accent-color-in-titlebar) {
           :root[tabsintitlebar]:not(:-moz-window-inactive):not(:-moz-lwtheme) {
             background-color: -moz-win-accentcolor;
             --titlebar-text-color: -moz-win-accentcolortext;
           }
         }
 %endif
 
         :root[tabsintitlebar] .tab-label:-moz-window-inactive {

--- a/dom/base/nsGkAtomList.h
+++ b/dom/base/nsGkAtomList.h
@@ -2236,17 +2236,17 @@ GK_ATOM(forcemessagemanager, "forcemessa
 // Names for system metrics
 GK_ATOM(color_picker_available, "color-picker-available")
 GK_ATOM(scrollbar_start_backward, "scrollbar-start-backward")
 GK_ATOM(scrollbar_start_forward, "scrollbar-start-forward")
 GK_ATOM(scrollbar_end_backward, "scrollbar-end-backward")
 GK_ATOM(scrollbar_end_forward, "scrollbar-end-forward")
 GK_ATOM(scrollbar_thumb_proportional, "scrollbar-thumb-proportional")
 GK_ATOM(overlay_scrollbars, "overlay-scrollbars")
-GK_ATOM(windows_accent_color_applies, "windows-accent-color-applies")
+GK_ATOM(windows_accent_color_in_titlebar, "windows-accent-color-in-titlebar")
 GK_ATOM(windows_default_theme, "windows-default-theme")
 GK_ATOM(mac_graphite_theme, "mac-graphite-theme")
 GK_ATOM(mac_yosemite_theme, "mac-yosemite-theme")
 GK_ATOM(windows_compositor, "windows-compositor")
 GK_ATOM(windows_glass, "windows-glass")
 GK_ATOM(touch_enabled, "touch-enabled")
 GK_ATOM(menubar_drag, "menubar-drag")
 GK_ATOM(swipe_animation_enabled, "swipe-animation-enabled")
@@ -2266,17 +2266,17 @@ GK_ATOM(windows_theme_generic, "windows-
 // And the same again, as media query keywords.
 GK_ATOM(_moz_color_picker_available, "-moz-color-picker-available")
 GK_ATOM(_moz_scrollbar_start_backward, "-moz-scrollbar-start-backward")
 GK_ATOM(_moz_scrollbar_start_forward, "-moz-scrollbar-start-forward")
 GK_ATOM(_moz_scrollbar_end_backward, "-moz-scrollbar-end-backward")
 GK_ATOM(_moz_scrollbar_end_forward, "-moz-scrollbar-end-forward")
 GK_ATOM(_moz_scrollbar_thumb_proportional, "-moz-scrollbar-thumb-proportional")
 GK_ATOM(_moz_overlay_scrollbars, "-moz-overlay-scrollbars")
-GK_ATOM(_moz_windows_accent_color_applies, "-moz-windows-accent-color-applies")
+GK_ATOM(_moz_windows_accent_color_in_titlebar, "-moz-windows-accent-color-in-titlebar")
 GK_ATOM(_moz_windows_default_theme, "-moz-windows-default-theme")
 GK_ATOM(_moz_mac_graphite_theme, "-moz-mac-graphite-theme")
 GK_ATOM(_moz_mac_yosemite_theme, "-moz-mac-yosemite-theme")
 GK_ATOM(_moz_windows_compositor, "-moz-windows-compositor")
 GK_ATOM(_moz_windows_classic, "-moz-windows-classic")
 GK_ATOM(_moz_windows_glass, "-moz-windows-glass")
 GK_ATOM(_moz_windows_theme, "-moz-windows-theme")
 GK_ATOM(_moz_os_version, "-moz-os-version")

--- a/layout/style/nsCSSRuleProcessor.cpp
+++ b/layout/style/nsCSSRuleProcessor.cpp
@@ -1127,19 +1127,19 @@ nsCSSRuleProcessor::InitSystemMetrics()
     sSystemMetrics->AppendElement(nsGkAtoms::mac_graphite_theme);
   }
 
   rv = LookAndFeel::GetInt(LookAndFeel::eIntID_MacYosemiteTheme, &metricResult);
   if (NS_SUCCEEDED(rv) && metricResult) {
     sSystemMetrics->AppendElement(nsGkAtoms::mac_yosemite_theme);
   }
 
-  rv = LookAndFeel::GetInt(LookAndFeel::eIntID_WindowsAccentColorApplies, &metricResult);
+  rv = LookAndFeel::GetInt(LookAndFeel::eIntID_WindowsAccentColorInTitlebar, &metricResult);
   if (NS_SUCCEEDED(rv) && metricResult) {
-    sSystemMetrics->AppendElement(nsGkAtoms::windows_accent_color_applies);
+    sSystemMetrics->AppendElement(nsGkAtoms::windows_accent_color_in_titlebar);
   }
 
   rv = LookAndFeel::GetInt(LookAndFeel::eIntID_DWMCompositor, &metricResult);
   if (NS_SUCCEEDED(rv) && metricResult) {
     sSystemMetrics->AppendElement(nsGkAtoms::windows_compositor);
   }
 
   rv = LookAndFeel::GetInt(LookAndFeel::eIntID_WindowsGlass, &metricResult);

--- a/layout/style/nsMediaFeatures.cpp
+++ b/layout/style/nsMediaFeatures.cpp
@@ -689,21 +689,21 @@ nsMediaFeatures::features[] = {
     &nsGkAtoms::_moz_mac_yosemite_theme,
     nsMediaFeature::eMinMaxNotAllowed,
     nsMediaFeature::eBoolInteger,
     nsMediaFeature::eNoRequirements,
     { &nsGkAtoms::mac_yosemite_theme },
     GetSystemMetric
   },
   {
-    &nsGkAtoms::_moz_windows_accent_color_applies,
+    &nsGkAtoms::_moz_windows_accent_color_in_titlebar,
     nsMediaFeature::eMinMaxNotAllowed,
     nsMediaFeature::eBoolInteger,
     nsMediaFeature::eNoRequirements,
-    { &nsGkAtoms::windows_accent_color_applies },
+    { &nsGkAtoms::windows_accent_color_in_titlebar },
     GetSystemMetric
   },
   {
     &nsGkAtoms::_moz_windows_compositor,
     nsMediaFeature::eMinMaxNotAllowed,
     nsMediaFeature::eBoolInteger,
     nsMediaFeature::eNoRequirements,
     { &nsGkAtoms::windows_compositor },

--- a/layout/style/test/test_media_queries.html
+++ b/layout/style/test/test_media_queries.html
@@ -623,81 +623,81 @@ function run() {
   expression_should_be_parseable("-moz-scrollbar-start-forward");
   expression_should_be_parseable("-moz-scrollbar-end-backward");
   expression_should_be_parseable("-moz-scrollbar-end-forward");
   expression_should_be_parseable("-moz-scrollbar-thumb-proportional");
   expression_should_be_parseable("-moz-overlay-scrollbars");
   expression_should_be_parseable("-moz-windows-default-theme");
   expression_should_be_parseable("-moz-mac-graphite-theme");
   expression_should_be_parseable("-moz-mac-yosemite-theme");
-  expression_should_be_parseable("-moz-windows-accent-color-applies");
+  expression_should_be_parseable("-moz-windows-accent-color-in-titlebar");
   expression_should_be_parseable("-moz-windows-compositor");
   expression_should_be_parseable("-moz-windows-classic");
   expression_should_be_parseable("-moz-windows-glass");
   expression_should_be_parseable("-moz-touch-enabled");
   expression_should_be_parseable("-moz-swipe-animation-enabled");
 
   expression_should_be_parseable("-moz-scrollbar-start-backward: 0");
   expression_should_be_parseable("-moz-scrollbar-start-forward: 0");
   expression_should_be_parseable("-moz-scrollbar-end-backward: 0");
   expression_should_be_parseable("-moz-scrollbar-end-forward: 0");
   expression_should_be_parseable("-moz-scrollbar-thumb-proportional: 0");
   expression_should_be_parseable("-moz-overlay-scrollbars: 0");
   expression_should_be_parseable("-moz-windows-default-theme: 0");
   expression_should_be_parseable("-moz-mac-graphite-theme: 0");
   expression_should_be_parseable("-moz-mac-yosemite-theme: 0");
-  expression_should_be_parseable("-moz-windows-accent-color-applies: 0");
+  expression_should_be_parseable("-moz-windows-accent-color-in-titlebar: 0");
   expression_should_be_parseable("-moz-windows-compositor: 0");
   expression_should_be_parseable("-moz-windows-classic: 0");
   expression_should_be_parseable("-moz-windows-glass: 0");
   expression_should_be_parseable("-moz-touch-enabled: 0");
   expression_should_be_parseable("-moz-swipe-animation-enabled: 0");
 
   expression_should_be_parseable("-moz-scrollbar-start-backward: 1");
   expression_should_be_parseable("-moz-scrollbar-start-forward: 1");
   expression_should_be_parseable("-moz-scrollbar-end-backward: 1");
   expression_should_be_parseable("-moz-scrollbar-end-forward: 1");
   expression_should_be_parseable("-moz-scrollbar-thumb-proportional: 1");
   expression_should_be_parseable("-moz-overlay-scrollbars: 1");
   expression_should_be_parseable("-moz-windows-default-theme: 1");
   expression_should_be_parseable("-moz-mac-graphite-theme: 1");
   expression_should_be_parseable("-moz-mac-yosemite-theme: 1");
-  expression_should_be_parseable("-moz-windows-accent-color-applies: 1");
+  expression_should_be_parseable("-moz-windows-accent-color-in-titlebar: 1");
   expression_should_be_parseable("-moz-windows-compositor: 1");
   expression_should_be_parseable("-moz-windows-classic: 1");
   expression_should_be_parseable("-moz-windows-glass: 1");
   expression_should_be_parseable("-moz-touch-enabled: 1");
   expression_should_be_parseable("-moz-swipe-animation-enabled: 1");
 
   expression_should_not_be_parseable("-moz-scrollbar-start-backward: -1");
   expression_should_not_be_parseable("-moz-scrollbar-start-forward: -1");
   expression_should_not_be_parseable("-moz-scrollbar-end-backward: -1");
   expression_should_not_be_parseable("-moz-scrollbar-end-forward: -1");
   expression_should_not_be_parseable("-moz-scrollbar-thumb-proportional: -1");
   expression_should_not_be_parseable("-moz-overlay-scrollbars: -1");
   expression_should_not_be_parseable("-moz-windows-default-theme: -1");
   expression_should_not_be_parseable("-moz-mac-graphite-theme: -1");
   expression_should_not_be_parseable("-moz-mac-yosemite-theme: -1");
-  expression_should_not_be_parseable("-moz-windows-accent-color-applies: -1");
+  expression_should_not_be_parseable("-moz-windows-accent-color-in-titlebar: -1");
   expression_should_not_be_parseable("-moz-windows-compositor: -1");
   expression_should_not_be_parseable("-moz-windows-classic: -1");
   expression_should_not_be_parseable("-moz-windows-glass: -1");
   expression_should_not_be_parseable("-moz-touch-enabled: -1");
   expression_should_not_be_parseable("-moz-swipe-animation-enabled: -1");
 
   expression_should_not_be_parseable("-moz-scrollbar-start-backward: true");
   expression_should_not_be_parseable("-moz-scrollbar-start-forward: true");
   expression_should_not_be_parseable("-moz-scrollbar-end-backward: true");
   expression_should_not_be_parseable("-moz-scrollbar-end-forward: true");
   expression_should_not_be_parseable("-moz-scrollbar-thumb-proportional: true");
   expression_should_not_be_parseable("-moz-overlay-scrollbars: true");
   expression_should_not_be_parseable("-moz-windows-default-theme: true");
   expression_should_not_be_parseable("-moz-mac-graphite-theme: true");
   expression_should_not_be_parseable("-moz-mac-yosemite-theme: true");
-  expression_should_not_be_parseable("-moz-windows-accent-color-applies: true");
+  expression_should_not_be_parseable("-moz-windows-accent-color-in-titlebar: true");
   expression_should_not_be_parseable("-moz-windows-compositor: true");
   expression_should_not_be_parseable("-moz-windows-classic: true");
   expression_should_not_be_parseable("-moz-windows-glass: true");
   expression_should_not_be_parseable("-moz-touch-enabled: true");
   expression_should_not_be_parseable("-moz-swipe-animation-enabled: true");
 
   // windows theme media queries
   expression_should_be_parseable("-moz-windows-theme: aero");

--- a/widget/LookAndFeel.h
+++ b/widget/LookAndFeel.h
@@ -244,17 +244,17 @@ public:
 
     /*
      * A Boolean value to determine whether the Windows accent color
      * should be applied to the title bar.
      *
      * The value of this metric is not used on other platforms. These platforms
      * should return NS_ERROR_NOT_IMPLEMENTED when queried for this metric.
      */
-    eIntID_WindowsAccentColorApplies,
+    eIntID_WindowsAccentColorInTitlebar,
 
     /*
      * A Boolean value to determine whether the Windows default theme is
      * being used.
      *
      * The value of this metric is not used on other platforms. These platforms
      * should return NS_ERROR_NOT_IMPLEMENTED when queried for this metric.
      */

--- a/widget/windows/nsLookAndFeel.cpp
+++ b/widget/windows/nsLookAndFeel.cpp
@@ -262,18 +262,16 @@ nsLookAndFeel::NativeGetColor(ColorID aI
     case eColorID__moz_cellhighlight:
       idx = COLOR_3DFACE;
       break;
     case eColorID__moz_win_accentcolor:
       res = GetAccentColor(aColor);
       if (NS_SUCCEEDED(res)) {
         return res;
       }
-      NS_WARNING("Using fallback for accent color - UI code failed to use the "
-                 "-moz-windows-accent-color-applies media query properly");
       // Seems to be the default color (hardcoded because of bug 1065998)
       aColor = NS_RGB(158, 158, 158);
       return NS_OK;
     case eColorID__moz_win_accentcolortext:
       res = GetAccentColorText(aColor);
       if (NS_SUCCEEDED(res)) {
         return res;
       }
@@ -435,20 +433,41 @@ nsLookAndFeel::GetIntImpl(IntID aID, int
 
     case eIntID_MacGraphiteTheme:
         aResult = 0;
         res = NS_ERROR_NOT_IMPLEMENTED;
         break;
     case eIntID_DWMCompositor:
         aResult = nsUXThemeData::CheckForCompositor();
         break;
-    case eIntID_WindowsAccentColorApplies:
+    case eIntID_WindowsAccentColorInTitlebar:
         {
           nscolor unused;
-          aResult = NS_SUCCEEDED(GetAccentColor(unused)) ? 1 : 0;
+          if (NS_WARN_IF(NS_FAILED(GetAccentColor(unused)))) {
+            aResult = 0;
+            break;
+          }
+
+          uint32_t colorPrevalence;
+          nsresult rv = mDwmKey->Open(nsIWindowsRegKey::ROOT_KEY_CURRENT_USER,
+                                      NS_LITERAL_STRING("SOFTWARE\\Microsoft\\Windows\\DWM"),
+                                      nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+          if (NS_WARN_IF(NS_FAILED(rv))) {
+            return rv;
+          }
+
+          // The ColorPrevalence value is set to 1 when the "Show color on title bar"
+          // setting in the Color section of Window's Personalization settings is
+          // turned on.
+          aResult =
+            (NS_SUCCEEDED(mDwmKey->ReadIntValue(NS_LITERAL_STRING("ColorPrevalence"),
+                                                &colorPrevalence)) &&
+             colorPrevalence == 1) ? 1 : 0;
+
+          mDwmKey->Close();
         }
         break;
     case eIntID_WindowsGlass:
         // Aero Glass is only available prior to Windows 8 when DWM is used.
         aResult = (nsUXThemeData::CheckForCompositor() && !IsWin8OrLater());
         break;
     case eIntID_AlertNotificationOrigin:
         aResult = 0;
@@ -784,23 +803,18 @@ nsLookAndFeel::GetAccentColor(nscolor& a
 
   rv = mDwmKey->Open(nsIWindowsRegKey::ROOT_KEY_CURRENT_USER,
                      NS_LITERAL_STRING("SOFTWARE\\Microsoft\\Windows\\DWM"),
                      nsIWindowsRegKey::ACCESS_QUERY_VALUE);
   if (NS_WARN_IF(NS_FAILED(rv))) {
     return rv;
   }
 
-  // The ColorPrevalence value is set to 1 when the "Show color on title bar"
-  // setting in the Color section of Window's Personalization settings is
-  // turned on.
-  uint32_t accentColor, colorPrevalence;
-  if (NS_SUCCEEDED(mDwmKey->ReadIntValue(NS_LITERAL_STRING("AccentColor"), &accentColor)) &&
-      NS_SUCCEEDED(mDwmKey->ReadIntValue(NS_LITERAL_STRING("ColorPrevalence"), &colorPrevalence)) &&
-      colorPrevalence == 1) {
+  uint32_t accentColor;
+  if (NS_SUCCEEDED(mDwmKey->ReadIntValue(NS_LITERAL_STRING("AccentColor"), &accentColor))) {
     // The order of the color components in the DWORD stored in the registry
     // happens to be the same order as we store the components in nscolor
     // so we can just assign directly here.
     aColor = accentColor;
     rv = NS_OK;
   } else {
     rv = NS_ERROR_NOT_AVAILABLE;
   }