See attached screenshot, the marking changes color at the column border. This needs the Oxygen style to reproduce, as it has hover effects.
Created attachment 42509 [details] Screenshot of the problem
View/delegate problem, so adding Steve to CC list.
I am not able to reproduce this. Maybe it has been fixed?
I can not re-test because for some reason the Oxygen style does not show up for me, and the bug only appeared in that style.