Show customer_grid indexer as green when realtime

Author: fredden

app/code/Magento/Indexer/Block/Backend/Grid/Column/Renderer/Scheduled.php

@@ -5,6 +5,8 @@
  */
 namespace Magento\Indexer\Block\Backend\Grid\Column\Renderer;
 
+use Magento\Customer\Model\Customer;
+
 /**
  * Renderer for 'Scheduled' column in indexer grid
  */
@@ -18,13 +20,35 @@ class Scheduled extends \Magento\Backend\Block\Widget\Grid\Column\Renderer\Abstr
      */
     public function render(\Magento\Framework\DataObject $row)
     {
+        if ($this->isPreferRealtime($row->getIndexerId())) {
+            $scheduleClass = 'grid-severity-major';
+            $realtimeClass = 'grid-severity-notice';
+        } else {
+            $scheduleClass = 'grid-severity-notice';
+            $realtimeClass = 'grid-severity-major';
+        }
+
         if ($this->_getValue($row)) {
-            $class = 'grid-severity-notice';
+            $class = $scheduleClass;
             $text = __('Update by Schedule');
         } else {
-            $class = 'grid-severity-major';
+            $class = $realtimeClass;
             $text = __('Update on Save');
         }
+
         return '<span class="' . $class . '"><span>' . $text . '</span></span>';
     }
+
+    /**
+     * Determine if an indexer is recommended to be in 'realtime' mode
+     *
+     * @param string $indexer
+     * @return bool
+     */
+    public function isPreferRealtime(string $indexer): bool
+    {
+        return in_array($indexer, [
+            Customer::CUSTOMER_GRID_INDEXER_ID,
+        ]);
+    }
 }