@adamhurwitz.eth
1. Turn on the “Filter type” “Grayscale” [1]
2. In “Shortcuts” only select “Color Filters” and leave everything else unselected [2]
3. When you use the accessibility shortcut it will toggle grayscale on|off
a. Press the Touch ID 3 times
b. Or press "option" + "command" + "F5"
[1]: https://support.apple.com/guide/mac-help/change-display-colors-easier-onscreen-mchl11ddd4b3/mac
[2]: https://support.apple.com/guide/mac-help/quickly-turn-accessibility-features-on-or-off-mchlp2975/mac.