Change background color of one menubar item eg Help in blue

[Spitfire]

AFAIK you can change background color of all items in the menu bar but not some/specific items

QMenuBar:item { background-color: rgb(255, 37, 186); }

QMenuBar:item { background-color: rgb(255, 37, 186); }

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To do what you want you would need to inherit from menu bar and paint it the way you want.