--- a/browser/themes/shared/tabs.inc.css
+++ b/browser/themes/shared/tabs.inc.css
@@ -157,16 +157,20 @@
   100% { transform: translateX(100%); }
 }
 
 :root[sessionrestored] .tab-throbber[progress]::before {
   fill: var(--tab-loading-fill);
   opacity: 1;
 }
 
+#TabsToolbar[brighttext] .tabbrowser-tab:not([visuallyselected=true]) {
+  --tab-loading-fill: #fff;
+}
+
 .tab-sharing-icon-overlay,
 .tab-icon-image {
   height: 16px;
   width: 16px;
 }
 
 .tab-throbber:not([pinned]),
 .tab-sharing-icon-overlay:not([pinned]),