after IOS 7 + upgrade, screen occasionally changes colors, lines, etc

I have a IPhone 5. After an upgrade, I noticed that I would have lines on my screen every once in awhile. Did search on internet which led to accessibility settings, but all of my settings are correct Couple months later, lines get worse, can go to a black screen, but phone / touch / camera works fine. other than the video going haywire once in awhile, the phone still works. When the display goes to 8 bit color, sometimes, I can't do anything, have to wait a minute and screen goes back and I can finish my IM. I reset my phone and the issue is still there. Don't know what it could be, any suggestions?