How to make a Cocoa Disclosure Triangle

I have most of the code that works

[self.开发者_如何学运维disclosureButton setBezelStyle:NSDisclosureBezelStyle];
[self.disclosureButton setButtonType: NSPushOnPushOffButton];
[self.disclosureButton setTitle:nil];
[self.disclosureButton highlight:NO];

However, when I press the button, it turns black to indicate the press. How do I get it to stop changing colors?

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The behavior you are seeing sounds correct for a Cocoa disclosure triangle, so I would say your code is successful.