There are times when you unknowingly enable some features on your iOS device and just don't know how to disable it. It had happened to me quite some times when I was new to the iOS ecosystem. In trying to learn how to use iPhone like a pro quickly, I would often mess up with the settings and wonder why I'm unable to fix some issues which would crop up now and then.
Just a couple of days back, my cousin bought an all new iPhone 6s. While he was trying to master iOS, the iPhone suddenly turned black and white. He thought something had horribly gone wrong on his iPhone when he couldn't solve the issue himself. Later, he told me the whole story with so much of disappointment. Having experienced the same problem myself, I instantly got the idea and was able to fix it right away.
There is a feature called Grayscale Mode in iOS, which turns the device screen into black and white. It comes with the suite of Accessibility and is developed for the people who are color blind or have vision difficulties.
You may have unknowingly enabled this mode on your device. Follow these steps to turn it off.
How to Fix an iPhone Stuck in Black and White Mode
Step #1. Launch Settings app on your iDevice → Tap on General.
Step #2. Tap on Accessibility.
Step #3. Turn off Grayscale.
Check Out Grayscale Zoom Filters
Simply double tap on your iPhone screen with three fingers to check if the zoom filters are causing the issue. In case you have enabled zoom filter, it will be disabled and so will be Grayscale mode.
Disable Grayscale Zoom Filter
Step #1. Open Settings app → Tap on General followed by Accessibility.
Step #2. Tap on Zoom.
Step #3. Scroll down and tap on Zoom Filter.
Step #4. Select None.
To prevent the issue from being repeated, it would be better to turn off Zoom. Hopefully, your device will no longer inadvertently turn into a Grayscale mode.