Ah, the Mac’s red, yellow, and green buttons: red for “close,” yellow for “minimize,” and green for “maximize” (sort of). You kind of get used to seeing them in that same red-yellow-green order. Until one day they’re all gray, like this:
Yuck. This is not nearly as good as red-yellow-green. If your Mac’s buttons are gray, and you want to bring back the color, just go to…
Apple menu/System Preferences/General
and choose “Blue” at the very top of that window. You probably would not expect to gain red, yellow, and green by choosing BLUE but that’s how it works. Choosing “Graphite” instead of “Blue” gives you the gray buttons. I know no one who likes the Graphite look but there it is.