message_list: Update recipient bar color on theme change.

web/src/message_lists.js

@@ -1,6 +1,7 @@
 import {Filter} from "./filter";
 import * as message_list from "./message_list";
 import * as recent_topics_util from "./recent_topics_util";
+import * as ui_util from "./ui_util";
 
 export let home;
 export let current;
@@ -30,4 +31,8 @@ export function initialize() {
         excludes_muted_topics: true,
     });
     current = home;
+
+    // For users with automatic color scheme, we need to detect change
+    // in `prefers-color-scheme`as it changes based on time.
+    ui_util.listener_for_preferred_color_scheme_change(update_recipient_bar_background_color);
 }