Customizing/reusing button style on Mojave

I'd like to use the appearance of system buttons (NSButton, NSSegmentedControl) as much as possible, however I need to modify certain aspects of their appearance. Particularly, the background color (for example use one of the system "Accent Colors" as a pemanent color for my button, not only when it's pressed). My goal is to create buttons that look identical to the system buttons, and make sure that my button appearance doesn't get out of sync if macOS changes its visual styles slightly in future updates.


Before Mojave, the only way to customize the buttons was to subclass NSButtonCell and in fact draw all fragments of the button appearance in code, from scratch. Is there any change in Mojave that would allow to better reuse the system appearance of buttons, and only modify it slightly?


If it's still necessary to redraw the button background in code, are there any image files in system frameworks that could be used for reference? Or are the button images drawn by the system in code, by applying vector shapes?