- (void)setButtonTitleFor:(NSButton*)button toString:(NSString*)title withColor:(NSColor*)color {
 NSMutableParagraphStyle *style = [[NSMutableParagraphStyle alloc] init];
 [style setAlignment:NSCenterTextAlignment];
 NSDictionary *attrsDictionary = [NSDictionary dictionaryWithObjectsAndKeys:
 color, NSForegroundColorAttributeName, style, NSParagraphStyleAttributeName, nil];
 NSAttributedString *attrString = [[NSAttributedString alloc]
 initWithString:title attributes:attrsDictionary];
 [button setAttributedTitle:attrString];
 [style release];
 [attrString release]; 
}

https://discussions.apple.com/message/9334854#9334854

A Modular method to set new text with color of an NSButton. Thanks go to the owner of this code - RayNewbie - in the Apple discussion forum.

Change Color of NSButton

mac

Objective C