There are many screen settings in Android. Options for brightness, contrast, color warmth, etc.
Monochrome or black and white are also part of these settings. To enable it:
1. Activate the mode developer.
2. Find and click on “Simulate anomaly” / “Simulate color space”.
3. Then, select “Monochrome Mode” / “Monochromacy” ”.
On Android 9, there is an icon in the curtain editor “Reading Mode” / “Reading More”, move it to a convenient place and you can easily turn on and off the black and white mode.
Note: The name and location of the settings may differ depending on the firmware of the device.