Issue #3479518 by xmacinfo: Switching color scheme may not take effect until clear cache

src/Form/SettingsForm.php

@@ -52,5 +52,11 @@ class SettingsForm extends ConfigFormBase {
     $this->config('xnavigation.settings')
       ->set('color_scheme', $form_state->getValue('color_scheme'))
       ->save();
+
+    // Clear all caches to apply the new color scheme.
+    \Drupal::service('cache.render')->invalidateAll(); // Clears the render cache.
+    \Drupal::service('cache.page')->invalidateAll();   // Clears the page cache.
+
+    \Drupal::service('theme.registry')->reset();
   }
 }