How can I change my iPhone display to black and white in iOS 8?
iOS 8 allows you to change your display to black and white, also known as grayscale. To put your iPhone in grayscale mode, simply go to Settings -> General -> Accessibility and toggle the Grayscale switch to on.
Note that this feature is only available in iOS 8. If you have iOS 7 you will need this jailbreak tweak to go to black and white.