How do you access the color panels that you mentioned. You said something about a your phone app but idk where that would be or where to search. If you could clearify that, then that would be splendid.
Green vertical line appeared a few hours ago.
@Maesteoguido's solution worked on my S7. Thanks
I also thought the black did not respond.
I repeated several times and restarted twice.
Screen is now back to normal.