Not sure I would make the "disabled" buttons stand out more brightly than a regular button. In fact I would swap the colors of those buttons, or maybe make the disabled button greyed out.
edit: hatchings make the inner text unreadable, I'll play around with opacity and dotted lines, thank you to the users who proposed them.
edit 2: went with dashed lines and published a new version. It even shaves off a couple of bytes off the minimized version :D
With good reason, IMO — too much contrast and it’s not clear that an element is disabled.
If you let a designer put grey on grey once, they’ll do it 10,000,000 times.