I had this same problem after I took my tab 3 (10") apart to check battery (not charging well). When I put it back together, wherever there was white on the screen it had static-like effect (multiple colored static). So I took it back apart and removed the display cable on one side where I could see copper (lead me to believe it was not in all the way).
The connectors actually have some sort of lever at the opposite side of where you insert cable. You need to pry that up (90 degrees), then insert the flat cable. Then once the cable is inserted all the way, press that plastic piece back down. When I did all that and turned it on, it was back to normal again (my screen was fine, no need to replace).
btw, the display cable is the one off by itself. There are three flat-ribbon cables when you open it up. 2 are off to one side and there is one by itself on the other side. It is the cable by itself that is the display cable.