Correct. Just similar to a line or dimension style. You change it, and every occurrance in the scene that used this global color updates.
Display color, layer color, materials color, …
In the UI, every ‘Select Color’ dialog panel (color wheel) would show the global color list next to the list of standard colors, I’d imagine.
It would also make sense, of course, to be able to import/export a set of colors, from the Rhino prefs. An office could have a set of colors they always use in their plan graphics, also referring to norms, maybe.
I use VisualArq a lot, which lets one choose color, linetype, pattern, … per object part. Yesterday I had to change many styles to the same color. I’d have to go through all of them again, manually, if I’d like to change it.
This would be in addition to ‘regular’, or non-global colors, of course. You don’t have to use them if you don’t need them.
In the DTP world, this has been a standard feature for many years. Adobe InDesign, Affinity Designer, CorelDraw, … all support global colors.