您可以使用 NSAttributedString 如下所示。

NSMutableAttributedString* string = [[NSMutableAttributedString alloc]initWithString:@"you string"];
[string addAttribute:NSFontAttributeName value:font range:NSMakeRange(0, string.length)];
[string addAttribute:NSForegroundColorAttributeName value:[UIColor blackColor] range:NSMakeRange(0, string.length)];//TextColor
[string addAttribute:NSUnderlineStyleAttributeName value:underlineNumber range:NSMakeRange(0, string.length)];//Underline color
[string addAttribute:NSUnderlineColorAttributeName value:[UIColor lightGrayColor] range:NSMakeRange(0, string.length)];//TextColor
 yourlabel. attributedText = string;

注意：您还可以将特定范围的字符串加下划线为喜欢这篇文章。另请注意，它仅适用于ios6 +。

Note: You can also underline particular range of string as like in this post. Also note down, it works ios6+ only.