Is there a grayscale mode for the Samsung Galaxy S5 (and other Samsung phones) on Marshmallow? The Marshmallow update for Samsung phones (mine is a Galaxy S5, but the Note series has the same problem) seems to have removed the ability to turn on grayscale mode when activating power saver mode.

Is there a way to re-enable this feature?
Samsung removed the feature from Power Saving, but you can still activate grayscale mode in the developer options.

Go to your Settings and into the Developer Options. 


If developer options isn't there, you have to manually activate the feature. Follow the steps in this answer.


Scroll to the Hardware-accelerated rendering section, and click on Simulate color space. Then select Monochromacy. Your phone is now in grayscale mode.

This color space option also exists on other phones.