red foreground on error

    static void registerListeners(final SwingOutputFieldRenderer renderer, final JTextField textField) {        if(renderer != null && textField != null) {            textField.getDocument().addDocumentListener(new DocumentListener() {                public void insertUpdate(DocumentEvent event) {                    send(event);                    textField.setForeground(Color.black);                }                public void removeUpdate(DocumentEvent event) {                    send(event);                    textField.setForeground(Color.black);                }                public void changedUpdate(DocumentEvent event) {                    send(event);                }                private void send(DocumentEvent event) {                    Document doc = event.getDocument();                    InputEditEvent evt = doc.getLength() == 0 ? InputEditEvent.EMPTY : InputEditEvent.FULL;                    renderer.notifyInputEditListeners(evt);                }            });            textField.addFocusListener(new FocusAdapter() {                public void focusLost(FocusEvent fe) {                   textField.setForeground(Color.black);                }            });        }    }