[WorldMaker]

Microsoft added it to the Windows 10 platform already, so I would suspect mobile should get it when it the fork merges back (mobile is currently an RS2 [CU] fork, not quite feature par with RS3 [FCU], and supposedly sometime after RS4 the platform should remerge as the CShell and other efforts move along).

Related: on any Windows 10 device updated to the FCU the shortcut key Win+Ctrl+C switches the current Ease of Access color filter (which defaults to grayscale) on/off immediately. It was making the rounds recently as one of those quick "confuse a coworker" pranks like the monitor orientation keyboard shortcuts.

The Insider builds are showing a lot of interesting work going into a rules engine for Quiet Hours which in recent builds was renamed to Focus Assist. Grayscale might be a good suggestion for Focus Assist rules, especially if the Focus Assist rules engine also takes over Night Light functionality (which I don't know if has been mentioned yet, and my Insider tablet was in the process of updating through a couple weeks of updates when I last left it).