Invert colors stuck as default?

I've got an iPhone and the invert colors are stuck as default (when I turn on invert colors, it goes back to normal) how do I fix this?

A glitch of some sort. This should fix it---Tap Settings on Home screen. Tap on General. Then tap on Reset. Reset Settings

It's part of the he accessibility settings. Someone is playing a prank on you or you clicked it by accident.