ipad screen background turns black and lettering is white

My ipad all of a sudden without any commands turned to a black background and the lettering is white. Icons and wallpaper are transparent like a negative. Apple guy had me restore it and it solved problem, but am now leary of putting much on it for fear of loosing it. I had to start from ground zero with it. Has anyone had problems like this???

This has been doing this for a long time now and is a bit frustrating. It's just happens randomly and then you have to touch the screen and it returns to normal.