My iPhone 6 has suddenly turned negative and touch is unresponsive?

I was just watching youtube on my iPhone 6 when the screen suddenly turned negative and unresponsive to touch! I've restarted my phone twice (by pressing the lock button and home button at the same time) but it's still unresponsive and negative when it restarts! Has anyone had this issue before and how did they fix it?!

Added (1). ok, nevermind… It's now suddenly back to normal after i just left it alone… Saves me money going to the repair shop, i guess.

Might just need to take it in to the repair shop

You should probably take it in to an Apple store or the place you got it from if you still have warranty on it

You need to consult the nearest Apple Store, they will guide you better and In case you need some serious security you can use Leo Privacy Guard for it.