Update: The Night Shift toggle was removed from Control Center in iOS 11. Click here to learn how to manually enable it in iOS 11 or later.
There are two ways to manually disable Night Shift mode if you accidently enabled it or want to bypass your normally scheduled time for it to activate itself. The easiest way is to swipe up from your Home screen to open Control Center, then tap the little sun/moon icon. This will temporarily disable Night Shift until your next scheduled activation time. To permanently disable Night Shift mode navigate to Settings > Display & Brightness > Night Shift and tap the "Scheduled" slider so it is WHITE / OFF.