diff --git a/browser/base/content/test/forms/browser_selectpopup_colors.js b/browser/base/content/test/forms/browser_selectpopup_colors.js
index d4fc7e157db1..a79790f651fc 100644
--- a/browser/base/content/test/forms/browser_selectpopup_colors.js
+++ b/browser/base/content/test/forms/browser_selectpopup_colors.js
@@ -70,7 +70,7 @@ const TRANSLUCENT_SELECT_APPLIES_ON_BASE_COLOR =
 const DISABLED_OPTGROUP_AND_OPTIONS =
   "<html><head>" +
   "<body><select id='one'>" +
-  '  <optgroup label=\'{"color": "rgb(0, 0, 0)", "backgroundColor": "buttonface"}\'>' +
+  '  <optgroup label=\'{"color": "rgb(0, 0, 0)", "backgroundColor": "rgba(0, 0, 0, 0)"}\'>' +
   '    <option disabled="">{"color": "GrayText", "backgroundColor": "rgba(0, 0, 0, 0)"}</option>' +
   '    <option>{"color": "rgb(0, 0, 0)", "backgroundColor": "rgba(0, 0, 0, 0)"}</option>' +
   '    <option disabled="">{"color": "GrayText", "backgroundColor": "rgba(0, 0, 0, 0)"}</option>' +
@@ -79,7 +79,7 @@ const DISABLED_OPTGROUP_AND_OPTIONS =
   '    <option>{"color": "rgb(0, 0, 0)", "backgroundColor": "rgba(0, 0, 0, 0)"}</option>' +
   '    <option>{"color": "rgb(0, 0, 0)", "backgroundColor": "rgba(0, 0, 0, 0)"}</option>' +
   "  </optgroup>" +
-  '  <optgroup label=\'{"color": "GrayText", "backgroundColor": "buttonface"}\' disabled=\'\'>' +
+  '  <optgroup label=\'{"color": "GrayText", "backgroundColor": "rgba(0, 0, 0, 0)"}\' disabled=\'\'>' +
   '    <option>{"color": "GrayText", "backgroundColor": "rgba(0, 0, 0, 0)"}</option>' +
   '    <option>{"color": "GrayText", "backgroundColor": "rgba(0, 0, 0, 0)"}</option>' +
   '    <option>{"color": "GrayText", "backgroundColor": "rgba(0, 0, 0, 0)"}</option>' +
@@ -447,11 +447,6 @@ add_task(async function test_translucent_select_applies_on_base_color() {
 });
 
 add_task(async function test_disabled_optgroup_and_options() {
-  // The colors used by this test are platform-specific.
-  if (AppConstants.platform != "win") {
-    return;
-  }
-
   await testSelectColors(DISABLED_OPTGROUP_AND_OPTIONS, 17, {
     skipSelectColorTest: true,
   });
diff --git a/browser/themes/windows/browser.css b/browser/themes/windows/browser.css
index 7ae6b93d8712..2cb783a0deb6 100644
--- a/browser/themes/windows/browser.css
+++ b/browser/themes/windows/browser.css
@@ -875,10 +875,6 @@ panel[touchmode] .PanelUI-subView #appMenu-zoom-controls > .subviewbutton-iconic
   background-color: unset;
 }
 
-#ContentSelectDropdown > menupopup > menucaption {
-  background-color: buttonface;
-}
-
 #ContentSelectDropdown > menupopup > menucaption[disabled="true"] {
   color: GrayText;
 }
