Today Elevenfour released the second wave of compatibility updates for selected styles to upgrade to WoltLab Suite 3.1.
You'll find general information on how to upgrade to WoltLab Suite 3.1 reading Elevenfour's Styles and Plugins for WoltLab Suite 3.1 - Compatibility and Update Tutorial - the first wave of updates includes the plugin "Elevenfour Language Package for Styles" and the styles "Basic Green", "Purify" and "Vind". There are no new features included - all updates are pure compatibility updates for WoltLab Suite 3.1. New variables and the profile cover photo are supported, of course.
If you're using Vind you'll notice that the SCSS-Code concerning the Redactor Editor was removed - its colors are now controlled using the color palette.