@furgo16 this isn't exactly what you asked for but you can hack the colour changes to be only checked/unchecked, I personally like to be able to see all three states, On (green), Off but available (red) and unavailable (transparent).

With it all being Python you don't need to compile to test, see main...Syres916:FreeCAD:Draft_Grid_Observer for changes (ignore the CMakeLists.txt change). My personal stylesheet picks up the checked/unchecked for the menu icon to automatically update:

QMenu::icon:checked { /* appearance of a 'checked' icon */
    background: #469143;
    border: 2px #469143;
    position: absolute;
    border-radius: 2px;
}

QMenu::icon:unchecked { /* appearance of a 'unchecked' icon */
    background: #914343;
    border: 2px #914343;
    position: absolute;
    border-radius: 2px;
}

@Syres916 oh, wow, thanks! Except for the colors, that was exactly what I was looking for. A few notes/questions after testing your branch, and using the Classic theme:

1. The tooltips on the button get the same background color as the button, which is probably not intended. That is, when the button is red, the tooltip is red as well. When the button is green, the tooltip is green too.
2. I think the color choice, whichever the color, is very personal, so I'd suggest going with defaults first. To me, having a red icon on the toolbar is having something that constantly seeks my attention, like a warning light on a car's dashboard :-)
3. I've not tried to change the colors with a custom stylesheet, as I'm not familiar with how they work with FreeCAD. Therefore I cannot comment much on that part, other than expressing the opinion that probably the default in the code should be to set the Classic theme colors for checked/unchecked toggle button, and let the stylesheet override that if the user wants to.
4. In which situation would the "unavailable (transparent)" be triggered?

Let me know if there is anything I can do to help if you're planning to submit a PR.

@furgo16 I've updated the branch to be just enabled/disabled and checked/unchecked so any colours only come from the user's stylesheet which deals with 1, 2 and 3.

With regard to question 4, the command should not be available when the mdi area is not the editable 3D view, in other words no open project, Techdraw sheet in view etc should disable the Toggle_Grid command.

To be honest I nolonger try to get involved in PR's with regard to subjective matters the agro isn't worth it for me. You're welcome to cherry pick any of my code and submit your own solution, I think there will be some return lines need adding to my code to satisfy the maintainers and stop some Lint warnings/errors being raised.

Thanks! I'll look into it in the next few days. Happy to submit the PR from that code, if that helps getting it merged for everyone.