I see this post is from a little bit ago have you been able to achieve the desired result? I have not personally seen this precise use case done in Tableau. What is the frequency the data is being updated?
One potential solution would be to highlight the data based on a date. Example: If the data updates every 24 hours. Have the viz highlight all the data points from the last 24hrs.
First question: how do you determine "New Data" ?