--- a/toolkit/themes/shared/in-content/common.inc.css
+++ b/toolkit/themes/shared/in-content/common.inc.css
@@ -3,17 +3,17 @@
  * 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/. */
 %endif
 @namespace html "http://www.w3.org/1999/xhtml";
 @namespace xul "http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul";
 
 *|*:root {
   --in-content-page-color: #0c0c0d;
-  --in-content-page-background: #fafafc;
+  --in-content-page-background: #f9f9fa;
   --in-content-text-color: #0c0c0d;
   --in-content-selected-text: #fff;
   --in-content-header-border-color: #c8c8c8;
   --in-content-box-background: #fff;
   --in-content-box-background-odd: #f3f6fa;
   --in-content-box-background-hover: #ebebeb;
   --in-content-box-background-active: #dadada;
   --in-content-box-border-color: #c1c1c1;
@@ -631,17 +631,17 @@ xul|*.radio-label-box {
   margin-inline-end: 8px;
   padding-inline-start: 0;
 }
 
 /* Category List */
 
 *|*#categories {
   -moz-appearance: none;
-  background-color: var(--in-content-page-background);
+  background-color: initial; /* override the background-color set on all richlistboxes in common.inc.css */
   padding-top: 70px;
   margin: 0;
   border-width: 0;
 }
 
 *|*.category {
   width: 240px;
   min-height: 48px;