https://wccftech.com/windows-10-rs5-build-17711/

Microsoft has started to roll out Windows 10 RS5 Insider Preview Build 17711 to Fast Ring and Skip Ahead Insiders. Today’s Preview brings the following new features and improvements to Redstone 5 testers.

Learning tools get richer: Under learning tools available on Reading View, you can now see additional themes. These let you choose the theme color which is best for your eyes.