change triangle button color on future theme

packages/app/src/styles/theme/future.scss

@@ -109,4 +109,22 @@ html[dark] {
     color: #95abba;
     background-color: #1f1f22;
   }
+
+  /*
+ * GROWI Sidebar
+ */
+  .grw-sidebar {
+    // Pagetree
+    .grw-pagetree {
+      @include override-list-group-item-for-pagetree(
+        $color-list,
+        $bgcolor-sidebar-list-group,
+        $color-list-hover,
+        $bgcolor-list-hover,
+        $color-list-active,
+        lighten($bgcolor-list-hover, 5%),
+        $gray-600
+      );
+    }
+  }
 }