Funny screen On IPad Air 2 when access photo or video

Hello, I have some problem with my iPad, but I can’t speak English fluently.

I like to watch YouTube video or Netflix for a long time, I also often keep the screen on (paused) when I am doing something else. I remember that I had dropped my iPad for several times. But the screen was okay, until one day when I was watching YouTube video then accidentally my screens turn into funny color.

but I have googled and found the solution to turn on “reduce white” on this website. And it’s works!

but after several months, when I was watching Netflix, the screen started increased the contrast color it self. I tried to increased the “reduce white” rate but it’s didn’t work. Then I found out that the funny contrast color only appeared when I am accessed photo, video, or game with many colors on it.