Changing the content to show a bot something different than regular user is always considered black hat and is frowned upon.
That being said, if you're trying to create different messages based on where the user came from, you may want to consider something like a bright box to provide direction and interaction to the visitor. Some general text in the page like that could be dynamic without being considered deceitful to Google.
I would have to recommend not trying to show Google something completely different than what users see in any regard.
