Screen turns pink after used for 30 minutes

I have noticed recently on my lenovo yoga 3 that after I use it for more than 30 minutes (sometimes less) the left side of the screen begins to turn a pinkish colour. I have figured that having dark colours on the screen doesn't cause the pink colour. When I have a white screen it happens quicker. If I use my laptop for long enough, the whole screen will have a pink tinge. Beneath the pink, I can see what was last on the screen. The screen turns back to normal when I leave my laptop off for an hour. How do I stop this from happening?