Also, just noticed that Windowblinds is not skinning all UWP apps. In fact, the Twitter app does not skin at all. Yet, other apps, such as the Windows store, skins just fine. Plus, when you click on the + to see the running apps in the tray, the background does not change color, it remains the standard Windows chosen color. And, the Windowblinds icon in the tray randomly will disappear. I've exited out of Windowblinds and reapplied several skins and still see the same issues.
The tray should pickup the skin setting for it. If you apply the corporate skin included with WindowBlinds does it then look different?
Regarding Twitter, thanks for reporting this. It appears they have done things a little unusually, but thats easily fixable so I will ensure that is addressed in the next beta update. Please let us know if you see any others with a similar issue.