Canon EOS 6D Mark II Mode D'emploi page 61

The description of menu functions hereafter assumes that you have
pressed the <M> button to display the menu screen.
You can also tap on the menu screen or turn the <6> or <5> dial to
operate the menu.
To cancel the operation, press the <M> button.
Dimmed Menu Items
Example: Highlight tone priority
3 Menu Operations and Configurations
Dimmed menu items cannot be set. The
menu item is dimmed if another function
setting is overriding it.
You can see the overriding function by
selecting the dimmed menu item and
pressing <0>.
If you cancel the overriding function's
setting, the dimmed menu item will
become settable.
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