About 4 days ago Whats new got updated and brought the white theme. Today again Whats new app was updated to 3.3.A.0.1 and this new updated brings the option to change the themes. So if you who didn't like the white theme of the What's new app now you can have the chance to change your theme to dark again. Its great for me as I personally didn't like the light theme on all the Xperia media Apps. You can go to What's New app settings and change the theme.