Change background color of ouput window

src/main/java/ChatClient.java

@@ -30,6 +30,7 @@ public class ChatClient extends JFrame implements KeyListener {
         outputTextArea = new JTextArea();
         outputTextArea.setEditable(false);
         outputTextArea.setBorder(BorderFactory.createTitledBorder("Chat"));
+        outputTextArea.setBackground(Color.lightGray);
 
         outputScrollPane = new JScrollPane(outputTextArea);