horizontal and vertical blue lines across screen, galaxy note 5 I have blue horizontal and vertical lines across my screen(galaxy note 5)
This happened once before and I was told to take it to best buy to refresh it.
It worked well for 5 months, but is back.

I would like to find out what is it and how do I get rid of it for good before I need to refresh again. 

I read online it could be developer options are on. I discovered how to shut it off, no change!
From your description, I believe we are talking about the "Universal Switch" feature.


  "A universal switch lets you designate certain touches or gestures to control specific actions on your phone..."


I had get in confidence with this unknown feature when my Samsung S6 was stuck, thus unresponsive, on this mysterious interface control. I finally got out of that hell by a "Power+Vol UP+Vol Down+Home" restart.

more on http://www.samsung.com/uk/accessibility/product_galaxy_universal_switch.html