--- a/browser/themes/linux/browser.css
+++ b/browser/themes/linux/browser.css
@@ -28,16 +28,19 @@
 
   --toolbarbutton-active-background: rgba(154,154,154,.5) linear-gradient(rgba(255,255,255,.7), rgba(255,255,255,.4));
   --toolbarbutton-active-bordercolor: rgba(0,0,0,.3);
   --toolbarbutton-active-boxshadow: 0 1px 1px rgba(0,0,0,.1) inset, 0 0 1px rgba(0,0,0,.3) inset;
 
   --toolbarbutton-checkedhover-backgroundcolor: rgba(200,200,200,.5);
 
   --panel-separator-color: ThreeDShadow;
+  --arrowpanel-dimmed: hsla(210,4%,10%,.07);
+  --arrowpanel-dimmed-further: hsla(210,4%,10%,.12);
+  --arrowpanel-dimmed-even-further: hsla(210,4%,10%,.17);
 
   --urlbar-separator-color: ThreeDShadow;
 }
 
 #menubar-items {
   -moz-box-orient: vertical; /* for flex hack */
 }
 
@@ -990,35 +993,35 @@ toolbaritem[cui-areatype="menu-panel"] >
 }
 
 #urlbar-zoom-button > .toolbarbutton-icon {
   display: none;
 }
 
 #urlbar-search-footer {
   border-top: 1px solid var(--panel-separator-color);
-  background-color: hsla(210,4%,10%,.07);
+  background-color: var(--arrowpanel-dimmed);
 }
 
 #urlbar-search-settings {
   -moz-appearance: none;
   -moz-user-focus: ignore;
   color: GrayText;
   margin: 0;
   border: 0;
   padding: 8px 20px;
   background: transparent;
 }
 
 #urlbar-search-settings:hover {
-  background-color: hsla(210,4%,10%,.07);
+  background-color: var(--arrowpanel-dimmed);
 }
 
 #urlbar-search-settings:hover:active {
-  background-color: hsla(210,4%,10%,.12);
+  background-color: var(--arrowpanel-dimmed-further);
 }
 
 #urlbar-search-splitter {
   -moz-appearance: none;
   width: 8px;
   margin-inline-start: -4px;
 }
 

--- a/browser/themes/linux/searchbar.css
+++ b/browser/themes/linux/searchbar.css
@@ -132,17 +132,17 @@ menuitem[cmd="cmd_clearhistory"][disable
 }
 
 .search-panel-tree {
   border-top: 1px solid var(--panel-separator-color) !important;
 }
 
 .search-panel-header {
   font-weight: normal;
-  background-color: hsla(210,4%,10%,.07);
+  background-color: var(--arrowpanel-dimmed);
   border: none;
   border-top: 1px solid var(--panel-separator-color);
   padding: 3px 5px;
   color: GrayText;
 }
 
 .search-panel-header > label {
   margin-top: 2px !important;
@@ -296,17 +296,17 @@ menuitem[cmd="cmd_clearhistory"][disable
 
 .search-setting-button {
   -moz-appearance: none;
   margin: 0;
   min-height: 32px;
 }
 
 .search-setting-button[selected] {
-  background-color: hsla(210,4%,10%,.15);
+  background-color: var(--arrowpanel-dimmed-further);
 }
 
 .search-setting-button-compact {
   list-style-image: url("chrome://browser/skin/gear.svg#gear");
 }
 
 .search-setting-button-compact[selected] {
   list-style-image: url("chrome://browser/skin/gear.svg#gear-inverted");

--- a/browser/themes/osx/browser.css
+++ b/browser/themes/osx/browser.css
@@ -39,16 +39,19 @@
   --urlbar-dropmarker-url: url("chrome://browser/skin/urlbar-history-dropmarker.png");
   --urlbar-dropmarker-region: rect(0, 11px, 14px, 0);
   --urlbar-dropmarker-active-region: rect(0, 22px, 14px, 11px);
   --urlbar-dropmarker-2x-url: url("chrome://browser/skin/urlbar-history-dropmarker@2x.png");
   --urlbar-dropmarker-2x-region: rect(0, 22px, 28px, 0);
   --urlbar-dropmarker-active-2x-region: rect(0, 44px, 28px, 22px);
 
   --panel-separator-color: hsla(210,4%,10%,.14);
+  --arrowpanel-dimmed: hsla(210,4%,10%,.07);
+  --arrowpanel-dimmed-further: hsla(210,4%,10%,.12);
+  --arrowpanel-dimmed-even-further: hsla(210,4%,10%,.17);
 
   --urlbar-separator-color: hsla(0,0%,16%,.2);
 }
 
 #urlbar:-moz-lwtheme:not([focused="true"]),
 .searchbar-textbox:-moz-lwtheme:not([focused="true"]) {
   opacity: .9;
 }
@@ -1703,33 +1706,33 @@ toolbar .toolbarbutton-1 > .toolbarbutto
 }
 
 #urlbar-zoom-button > .toolbarbutton-icon {
   display: none;
 }
 
 #urlbar-search-footer {
   border-top: 1px solid var(--panel-separator-color);
-  background-color: hsla(210,4%,10%,.07);
+  background-color: var(--arrowpanel-dimmed);
 }
 
 #urlbar-search-settings {
   -moz-appearance: none;
   -moz-user-focus: ignore;
   color: GrayText;
   margin: 0;
   padding: 8px 20px;
 }
 
 #urlbar-search-settings:hover {
-  background-color: hsla(210,4%,10%,.07);
+  background-color: var(--arrowpanel-dimmed);
 }
 
 #urlbar-search-settings:hover:active {
-  background-color: hsla(210,4%,10%,.12);
+  background-color: var(--arrowpanel-dimmed-further);
 }
 
 #urlbar-search-splitter {
   min-width: 8px;
   width: 8px;
   background-image: none;
   margin: 0 -4px;
   position: relative;

--- a/browser/themes/osx/searchbar.css
+++ b/browser/themes/osx/searchbar.css
@@ -122,17 +122,17 @@
 
 .search-panel-tree {
   border-top: 1px solid var(--panel-separator-color) !important;
 }
 
 .search-panel-header {
   font-size: 10px;
   font-weight: normal;
-  background-color: hsla(210,4%,10%,.07);
+  background-color: var(--arrowpanel-dimmed);
   border-top: 1px solid var(--panel-separator-color);
   margin: 0;
   padding: 3px 6px;
   color: GrayText;
 }
 
 .search-panel-header > label {
   margin-top: 2px !important;
@@ -278,17 +278,17 @@
 
 .search-setting-button {
   -moz-appearance: none;
   border-radius: 0 0 4px 4px;
   min-height: 32px;
 }
 
 .search-setting-button[selected] {
-  background-color: hsla(210,4%,10%,.15);
+  background-color: var(--arrowpanel-dimmed-further);
 }
 
 .search-setting-button-compact {
   list-style-image: url("chrome://browser/skin/gear.svg#gear");
 }
 
 .search-setting-button-compact[selected] {
   list-style-image: url("chrome://browser/skin/gear.svg#gear-inverted");

--- a/browser/themes/shared/controlcenter/panel.inc.css
+++ b/browser/themes/shared/controlcenter/panel.inc.css
@@ -151,21 +151,21 @@
 }
 
 .identity-popup-expander:-moz-focusring > .button-box,
 .identity-popup-expander[panel-multiview-anchor] > .button-box {
   border-style: none;
 }
 
 .identity-popup-expander:hover {
-  background-color: hsla(210,4%,10%,.07);
+  background-color: var(--arrowpanel-dimmed);
 }
 
 .identity-popup-expander:hover:active {
-  background-color: hsla(210,4%,10%,.12);
+  background-color: var(--arrowpanel-dimmed-further);
   box-shadow: 0 1px 0 hsla(210,4%,10%,.05) inset;
 }
 
 /* CONTENT */
 
 .identity-popup-permission-label,
 .identity-popup-permission-state-label,
 #identity-popup-security-content > description,
@@ -273,36 +273,36 @@
 }
 
 #identity-popup-securityView-body {
   padding-inline-end: 1em;
 }
 
 #identity-popup-securityView-footer {
   margin-top: 1em;
-  background-color: hsla(210,4%,10%,.07);
+  background-color: var(--arrowpanel-dimmed);
 }
 
 #identity-popup-securityView-footer > button {
   -moz-appearance: none;
   margin: 0;
   border: none;
   border-top: 1px solid var(--panel-separator-color);
   padding: 8px 20px;
   color: inherit;
   background-color: transparent;
 }
 
 #identity-popup-securityView-footer > button:hover,
 #identity-popup-securityView-footer > button:focus {
-  background-color: hsla(210,4%,10%,.07);
+  background-color: var(--arrowpanel-dimmed);
 }
 
 #identity-popup-securityView-footer > button:hover:active {
-  background-color: hsla(210,4%,10%,.12);
+  background-color: var(--arrowpanel-dimmed-further);
 }
 
 #identity-popup-content-verifier ~ description {
   margin-top: 1em;
   color: Graytext;
 }
 
 description#identity-popup-content-verified-by,

--- a/browser/themes/shared/customizableui/panelUI.inc.css
+++ b/browser/themes/shared/customizableui/panelUI.inc.css
@@ -402,17 +402,17 @@ toolbarpaletteitem:-moz-any([place="pale
   width: 16px;
   margin-inline-start: -16px;
   height: 51px;
   margin-bottom: 2.2em;
   padding: 0;
 }
 
 .panelUI-grid .toolbarbutton-1:not([buttonover])@buttonStateHover@ > .toolbarbutton-menubutton-dropmarker {
-  background-color: hsla(210,4%,10%,.1) !important;
+  background-color: var(--arrowpanel-dimmed) !important;
   border-radius: 0 0 0 2px;
 }
 
 .panelUI-grid .toolbarbutton-1:not([buttonover])@buttonStateHover@ > .toolbarbutton-menubutton-dropmarker:-moz-locale-dir(rtl) {
   border-radius: 0 0 2px 0;
 }
 
 #main-window:not([customizing]) .panel-combined-button[disabled] > .toolbarbutton-icon {
@@ -429,17 +429,17 @@ toolbaritem[cui-areatype="menu-panel"][s
   -moz-box-pack: center;
 }
 
 toolbaritem[cui-areatype="menu-panel"][sdkstylewidget="true"] > iframe {
   margin: 4px auto;
 }
 
 #PanelUI-multiView[viewtype="subview"] > .panel-viewcontainer > .panel-viewstack > .panel-mainview >  #PanelUI-mainView {
-  background-color: hsla(210,4%,10%,.1);
+  background-color: var(--arrowpanel-dimmed);
 }
 
 #PanelUI-multiView[viewtype="subview"] #PanelUI-mainView > #PanelUI-contents-scroller > #PanelUI-contents > .panel-wide-item,
 #PanelUI-multiView[viewtype="subview"] #PanelUI-mainView > #PanelUI-contents-scroller > #PanelUI-contents > .toolbarbutton-1:not([panel-multiview-anchor="true"]),
 #PanelUI-multiView[viewtype="subview"] #PanelUI-mainView > #PanelUI-footer > #PanelUI-update-status,
 #PanelUI-multiView[viewtype="subview"] #PanelUI-mainView > #PanelUI-footer > #PanelUI-footer-fxa > #PanelUI-fxa-status > #PanelUI-fxa-avatar,
 #PanelUI-multiView[viewtype="subview"] #PanelUI-mainView > #PanelUI-footer > #PanelUI-footer-fxa > #PanelUI-fxa-status > #PanelUI-fxa-label,
 #PanelUI-multiView[viewtype="subview"] #PanelUI-mainView > #PanelUI-footer > #PanelUI-footer-fxa > #PanelUI-fxa-icon,
@@ -530,48 +530,48 @@ toolbarpaletteitem[place="palette"] > to
 #zoom-reset-button > .toolbarbutton-icon {
   display: none;
 }
 
 #PanelUI-footer {
   display: flex;
   flex-shrink: 0;
   flex-direction: column;
-  background-color: hsla(210,4%,10%,.07);
+  background-color: var(--arrowpanel-dimmed);
   padding: 0;
   margin: 0;
 }
 
 #main-window[customizing] #PanelUI-footer-fxa {
   display: none;
 }
 
 #PanelUI-footer-fxa:not([fxastatus="signedin"]) > toolbarseparator,
 #PanelUI-footer-fxa:not([fxastatus="signedin"]) > #PanelUI-fxa-icon,
 #PanelUI-footer-fxa:not([fxaprofileimage]) > #PanelUI-fxa-status > #PanelUI-fxa-avatar {
   display: none;
 }
 
 #PanelUI-footer-fxa[fxastatus="error"] > #PanelUI-fxa-status::after {
   content: url(chrome://browser/skin/warning.svg);
-  filter: drop-shadow(0 1px 0 hsla(206, 50%, 10%, .15));
+  filter: drop-shadow(0 1px 0 hsla(206,50%,10%,.15));
   width: 47px;
   padding-top: 1px;
   display: block;
   text-align: center;
   position: relative;
   top: 25%;
 }
 
 #PanelUI-update-status[update-status]::after {
   content: "";
   width: 14px;
   height: 14px;
   margin-right: 16.5px;
-  box-shadow: 0px 1px 0px rgba(255, 255, 255, 0.2) inset, 0px -1px 0px rgba(0, 0, 0, 0.1) inset, 0px 1px 0px rgba(12, 27, 38, 0.2);
+  box-shadow: 0px 1px 0px rgba(255,255,255,.2) inset, 0px -1px 0px rgba(0,0,0,.1) inset, 0px 1px 0px rgba(12,27,38,.2);
   border-radius: 2px;
   background-size: contain;
   display: -moz-box;
 }
 
 #PanelUI-update-status[update-status="succeeded"]::after {
   background-image: url(chrome://browser/skin/update-badge.svg);
   background-color: #74BF43;
@@ -904,77 +904,77 @@ toolbarpaletteitem[place="palette"] > to
   opacity: 0.4;
 }
 
 #PanelUI-fxa-status:not([disabled]):hover,
 #PanelUI-fxa-icon:not([disabled]):hover,
 #PanelUI-help:not([disabled]):hover,
 #PanelUI-customize:hover,
 #PanelUI-quit:not([disabled]):hover {
-  outline: 1px solid hsla(210,4%,10%,.07);
-  background-color: hsla(210,4%,10%,.07);
+  outline: 1px solid var(--arrowpanel-dimmed);
+  background-color: var(--arrowpanel-dimmed);
 }
 
 #PanelUI-fxa-status:not([disabled]):hover:active,
 #PanelUI-fxa-icon:not([disabled]):hover:active,
 #PanelUI-help:not([disabled]):hover:active,
 #PanelUI-customize:hover:active,
 #PanelUI-quit:not([disabled]):hover:active {
-  outline: 1px solid hsla(210,4%,10%,.12);
-  background-color: hsla(210,4%,10%,.12);
+  outline: 1px solid var(--arrowpanel-dimmed-further);
+  background-color: var(--arrowpanel-dimmed-further);
   box-shadow: 0 1px 0 hsla(210,4%,10%,.05) inset;
 }
 
 #PanelUI-fxa-status:not([disabled]):hover,
 #PanelUI-fxa-status:not([disabled]):hover:active,
 #PanelUI-fxa-icon:not([disabled]):hover,
 #PanelUI-fxa-icon:not([disabled]):hover:active {
   outline: none;
 }
 
 #PanelUI-footer-fxa[fxastatus="error"] {
-  background-color: hsla(42, 94%, 88%, 1.0);
-  border-top: 1px solid hsla(42, 94%, 70%, 1.0);
+  background-color: hsl(42,94%,88%);
+  border-top: 1px solid hsl(42,94%,70%);
 }
 
 #PanelUI-footer-fxa[fxastatus="error"] > #PanelUI-fxa-status:hover {
-  background-color: hsla(42, 94%, 85%, 1.0);
+  background-color: hsl(42,94%,85%);
 }
 
 #PanelUI-footer-fxa[fxastatus="error"] > #PanelUI-fxa-status:hover:active {
-  background-color: hsla(42, 94%, 82%, 1.0);
+  background-color: hsl(42,94%,82%);
   box-shadow: 0 1px 0 hsla(210,4%,10%,.05) inset;
 }
 
 #PanelUI-update-status {
   color: black;
 }
 
 #PanelUI-update-status[update-status="succeeded"] {
-  background-color: hsla(96, 65%, 75%, 0.5);
+  background-color: hsla(96,65%,75%,.5);
 }
 
 #PanelUI-update-status[update-status="succeeded"]:not([disabled]):hover {
-  background-color: hsla(96, 65%, 75%, 0.8);
+  background-color: hsla(96,65%,75%,.8);
 }
 
 #PanelUI-update-status[update-status="succeeded"]:not([disabled]):hover:active {
-  background-color: hsl(96, 65%, 75%);
+  background-color: hsl(96,65%,75%);
 }
 
 #PanelUI-update-status[update-status="failed"] {
-  background-color: hsla(359, 69%, 84%, 0.5);
+  background-color: hsla(359,69%,84%,.5);
 }
 
 #PanelUI-update-status[update-status="failed"]:not([disabled]):hover {
-  background-color: hsla(359, 69%, 84%, 0.8);
+  background-color: hsla(359,69%,84%,.8);
 }
 
 #PanelUI-update-status[update-status="failed"]:not([disabled]):hover:active {
-  background-color: hsl(359, 69%, 84%);
+  background-color: hsl(359,69%,84%);
 }
 
 #PanelUI-quit:not([disabled]):hover {
   background-color: #d94141;
   outline-color: #c23a3a;
 }
 
 #PanelUI-quit:not([disabled]):hover:active {
@@ -1006,20 +1006,20 @@ toolbarpaletteitem[place="palette"] > to
 panelview .toolbarbutton-1,
 .subviewbutton,
 .widget-overflow-list .toolbarbutton-1,
 .panelUI-grid .toolbarbutton-1 > .toolbarbutton-menubutton-button,
 .share-provider-button,
 .toolbaritem-combined-buttons@inAnyPanel@ > toolbarbutton {
   -moz-appearance: none;
   padding: 0 6px;
-  background-color: hsla(210,4%,10%,0);
+  background-color: transparent;
   border-radius: 2px;
   border-style: solid;
-  border-color: hsla(210,4%,10%,0);
+  border-color: transparent;
 }
 
 panelview .toolbarbutton-1,
 .subviewbutton,
 .widget-overflow-list .toolbarbutton-1,
 .share-provider-button,
 .toolbaritem-combined-buttons@inAnyPanel@ > toolbarbutton {
   border-width: 1px;
@@ -1092,51 +1092,51 @@ panelview .toolbarbutton-1,
 
 panelview .toolbarbutton-1@buttonStateHover@,
 toolbarbutton.subviewbutton@buttonStateHover@,
 menu.subviewbutton@menuStateHover@,
 menuitem.subviewbutton@menuStateHover@,
 .share-provider-button@buttonStateHover@:not([checked="true"]),
 .widget-overflow-list .toolbarbutton-1@buttonStateHover@,
 .toolbaritem-combined-buttons@inAnyPanel@ > toolbarbutton@buttonStateHover@ {
-  background-color: hsla(210,4%,10%,.08);
-  border-color: hsla(210,4%,10%,.11);
+  background-color: var(--arrowpanel-dimmed);
+  border-color: var(--panel-separator-color);
 }
 
 .toolbaritem-combined-buttons@inAnyPanel@@buttonStateHover@ {
-  border-color: hsla(210,4%,10%,.11);
+  border-color: var(--panel-separator-color);
 }
 
 panelview .toolbarbutton-1:-moz-any(@buttonStateActive@,[checked=true]),
 toolbarbutton.subviewbutton@buttonStateActive@,
 menu.subviewbutton@menuStateActive@,
 menuitem.subviewbutton@menuStateActive@,
 .share-provider-button:-moz-any(@buttonStateActive@,[checked=true]),
 .widget-overflow-list .toolbarbutton-1@buttonStateActive@,
 .toolbaritem-combined-buttons@inAnyPanel@ > toolbarbutton@buttonStateActive@ {
-  background-color: hsla(210,4%,10%,.12);
+  background-color: var(--arrowpanel-dimmed-further);
   border-color: var(--panel-separator-color);
   box-shadow: 0 1px 0 hsla(210,4%,10%,.03) inset;
 }
 
 .subviewbutton.panel-subview-footer {
   margin: 4px -4px -4px;
-  background-color: hsla(210,4%,10%,.07);
+  background-color: var(--arrowpanel-dimmed);
   border-top: 1px solid var(--panel-separator-color);
   border-radius: 0;
 }
 
 menuitem.panel-subview-footer@menuStateHover@,
 .subviewbutton.panel-subview-footer@buttonStateHover@ {
-  background-color: hsla(210,4%,10%,.15);
+  background-color: var(--arrowpanel-dimmed-further);
 }
 
 menuitem.panel-subview-footer@menuStateActive@,
 .subviewbutton.panel-subview-footer@buttonStateActive@ {
-  background-color: hsla(210,4%,10%,.19);
+  background-color: var(--arrowpanel-dimmed-even-further);
   box-shadow: 0 1px 0 hsla(210,4%,10%,.05) inset;
 }
 
 #BMB_bookmarksPopup .subviewbutton {
   font: menu;
   font-weight: normal;
 }
 
@@ -1293,21 +1293,21 @@ toolbarpaletteitem[place="palette"] > .t
 }
 
 toolbarpaletteitem[place="palette"] > #search-container {
   min-width: 7em;
   width: 7em;
 }
 
 .toolbaritem-combined-buttons@inAnyPanel@ {
-  background-color: hsla(210,4%,10%,0);
+  background-color: transparent;
   border-radius: 2px;
   border: 1px solid;
-  border-color: hsla(210,4%,10%,0);
-  border-bottom-color: hsla(210,4%,10%,.1);
+  border-color: transparent;
+  border-bottom-color: var(--panel-separator-color);
   padding: 0;
   transition-property: background-color, border-color;
   transition-duration: 150ms;
 }
 
 /* Make direct siblings overlap borders: */
 .toolbaritem-combined-buttons + .toolbaritem-combined-buttons@inAnyPanel@ {
   border-top-color: transparent !important;
@@ -1476,17 +1476,17 @@ menuitem[checked="true"].subviewbutton >
 }
 
 #PanelUI-panicView.cui-widget-panelview {
   min-width: 280px;
 }
 
 #PanelUI-panic-timeframe {
   padding: 15px;
-  border-bottom: 1px solid rgba(0,0,0,0.1);
+  border-bottom: 1px solid var(--panel-separator-color);
 }
 
 #panic-button-success-icon,
 #PanelUI-panic-timeframe-icon,
 #PanelUI-panic-timeframe-icon-small {
   background-color: transparent;
   margin-inline-end: 10px;
 }
@@ -1535,24 +1535,24 @@ menuitem[checked="true"].subviewbutton >
   padding: 1px;
   margin: 0 0 2px;
   background-color: transparent;
   border-radius: 2px;
   border: 1px solid transparent;
 }
 
 .subviewradio@buttonStateHover@ {
-  background-color: hsla(210,4%,10%,.08);
+  background-color: var(--arrowpanel-dimmed);
   border-color: var(--panel-separator-color);
 }
 
 .subviewradio[selected],
 .subviewradio[selected]:hover,
 .subviewradio@buttonStateActive@ {
-  background-color: hsla(210,4%,10%,.12);
+  background-color: var(--arrowpanel-dimmed-further);
   border-color: var(--panel-separator-color);
   box-shadow: 0 1px 0 hsla(210,4%,10%,.03) inset;
 }
 
 .subviewradio > .radio-check {
   -moz-appearance: none;
   width: 16px;
   height: 16px;

--- a/browser/themes/shared/downloads/downloads.inc.css
+++ b/browser/themes/shared/downloads/downloads.inc.css
@@ -36,17 +36,17 @@
   padding: 16px 25px;
   margin: 0;
   /* The panel can be wider than this description after the blocked subview is
      shown, so center the text. */
   text-align: center;
 }
 
 .downloadsPanelFooter {
-  background-color: hsla(210,4%,10%,.07);
+  background-color: var(--arrowpanel-dimmed);
   border-top: 1px solid var(--panel-separator-color);
 }
 
 .downloadsPanelFooter toolbarseparator {
   margin: 0;
   border: 0;
   min-width: 0;
   border-left: 1px solid var(--panel-separator-color);
@@ -60,24 +60,24 @@
   margin: 0;
   padding: 0;
   min-width: 0;
   min-height: 40px;
   border: none;
 }
 
 .downloadsPanelFooterButton:hover {
-  outline: 1px solid hsla(210,4%,10%,.07);
-  background-color: hsla(210,4%,10%,.07);
+  outline: 1px solid var(--arrowpanel-dimmed);
+  background-color: var(--arrowpanel-dimmed);
 }
 
 .downloadsPanelFooterButton:hover:active,
 .downloadsPanelFooterButton[open="true"] {
-  outline: 1px solid hsla(210,4%,10%,.12);
-  background-color: hsla(210,4%,10%,.12);
+  outline: 1px solid var(--arrowpanel-dimmed-further);
+  background-color: var(--arrowpanel-dimmed-further);
   box-shadow: 0 1px 0 hsla(210,4%,10%,.05) inset;
 }
 
 .downloadsPanelFooterButton[default] {
   background-color: #0996f8;
   color: white;
 }
 

--- a/browser/themes/shared/plugin-doorhanger.inc.css
+++ b/browser/themes/shared/plugin-doorhanger.inc.css
@@ -21,18 +21,18 @@
   background-image: url("chrome://mozapps/skin/extensions/alerticon-info-negative.png");
   background-repeat: no-repeat;
   width: 16px;
   height: 15px;
   margin-inline-start: 6px;
 }
 
 .click-to-play-plugins-notification-button-container {
-  background-color: hsla(210,4%,10%,.07);
-  border-top: 1px solid hsla(210,4%,10%,.12);
+  background-color: var(--arrowpanel-dimmed);
+  border-top: 1px solid var(--panel-separator-color);
   padding: 10px;
   margin-top: 5px;
 }
 
 .click-to-play-popup-button {
   width: 50%;
 }
 

--- a/browser/themes/windows/browser.css
+++ b/browser/themes/windows/browser.css
@@ -41,16 +41,19 @@
   --urlbar-dropmarker-hover-region: rect(0px, 22px, 14px, 11px);
   --urlbar-dropmarker-active-region: rect(0px, 33px, 14px, 22px);
   --urlbar-dropmarker-2x-url: url("chrome://browser/skin/urlbar-history-dropmarker@2x.png");
   --urlbar-dropmarker-2x-region: rect(0, 22px, 28px, 0);
   --urlbar-dropmarker-hover-2x-region: rect(0, 44px, 28px, 22px);
   --urlbar-dropmarker-active-2x-region: rect(0, 66px, 28px, 44px);
 
   --panel-separator-color: ThreeDLightShadow;
+  --arrowpanel-dimmed: hsla(210,4%,10%,.07);
+  --arrowpanel-dimmed-further: hsla(210,4%,10%,.12);
+  --arrowpanel-dimmed-even-further: hsla(210,4%,10%,.17);
 
   --urlbar-separator-color: ThreeDLightShadow;
 }
 
 @media (-moz-windows-default-theme) {
   :root {
     --panel-separator-color: hsla(210,4%,10%,.14);
   }
@@ -1439,35 +1442,35 @@ html|*.urlbar-input:-moz-lwtheme::placeh
 }
 
 .search-go-container {
   padding: 2px 2px;
 }
 
 #urlbar-search-footer {
   border-top: 1px solid var(--panel-separator-color);
-  background-color: hsla(210,4%,10%,.07);
+  background-color: var(--arrowpanel-dimmed);
 }
 
 #urlbar-search-settings {
   -moz-appearance: none;
   -moz-user-focus: ignore;
   color: GrayText;
   margin: 0;
   border: 0;
   padding: 8px 20px;
   background: transparent;
 }
 
 #urlbar-search-settings:hover {
-  background-color: hsla(210,4%,10%,.07);
+  background-color: var(--arrowpanel-dimmed);
 }
 
 #urlbar-search-settings:hover:active {
-  background-color: hsla(210,4%,10%,.12);
+  background-color: var(--arrowpanel-dimmed-further);
 }
 
 #urlbar-search-splitter {
   min-width: 6px;
   margin-inline-start: -3px;
   border: none;
   background: transparent;
 }

--- a/browser/themes/windows/searchbar.css
+++ b/browser/themes/windows/searchbar.css
@@ -127,17 +127,17 @@
 }
 
 .search-panel-tree {
   border-top: 1px solid var(--panel-separator-color) !important;
 }
 
 .search-panel-header {
   font-weight: normal;
-  background-color: hsla(210,4%,10%,.07);
+  background-color: var(--arrowpanel-dimmed);
   border: none;
   border-top: 1px solid var(--panel-separator-color);
   margin: 0;
   padding: 3px 6px;
   color: GrayText;
 }
 
 .search-panel-header > label {
@@ -288,17 +288,17 @@
 }
 
 .search-setting-button {
   -moz-appearance: none;
   min-height: 32px;
 }
 
 .search-setting-button[selected] {
-  background-color: hsla(210,4%,10%,.15);
+  background-color: var(--arrowpanel-dimmed-further);
 }
 
 .search-setting-button-compact {
   list-style-image: url("chrome://browser/skin/gear.svg#gear");
 }
 
 .search-setting-button-compact[selected] {
   list-style-image: url("chrome://browser/skin/gear.svg#gear-inverted");