UILabel with text of two different colors

The way to do it is to use NSAttributedString like this:

NSMutableAttributedString *text = 
 [[NSMutableAttributedString alloc] 
   initWithAttributedString: label.attributedText];

[text addAttribute:NSForegroundColorAttributeName 
             value:[UIColor redColor] 
             range:NSMakeRange(10, 1)];
[label setAttributedText: text];

I created a UILabel extension to do it.