Currently, undoing changes made through the Visual sidebar (Cmd+Z) will undo all recent changes, but the editors will not update to show the new values. This should be fixed, as the ability to undo and see the changes is important to style editing.
<rdar://problem/22363373>
This is also being added at the same time as https://bugs.webkit.org/show_bug.cgi?id=148254. I will close this bug once it is confirmed to be working.
This was fixed in r194737.