var myString:NSString = "I AM KIRIT MODI"
var myMutableString = NSMutableAttributedString()
override func viewDidLoad() {

    myMutableString = NSMutableAttributedString(string: myString, attributes: [NSFontAttributeName:UIFont(name: "Georgia", size: 18.0)!])
    myMutableString.addAttribute(NSForegroundColorAttributeName, value: UIColor.redColor(), range: NSRange(location:2,length:4))
    // set label Attribute
    labName.attributedText = myMutableString
    super.viewDidLoad()
}

 myMutableString.addAttribute(NSForegroundColorAttributeName, value: UIColor.greenColor(), range: NSRange(location:10,length:5))

var myMutableString = NSMutableAttributedString()
var myString = "文章文章文章文章文章文章文章文章文章文章文章文章文章文章文章"
myMutableString = NSMutableAttributedString(string: myString, attributes: [NSFontAttributeName:UIFont.hiraginoSans(ofSize: 12)])
myMutableString.addAttribute(NSForegroundColorAttributeName, value: Color.gray, range: NSRange(location:7,length:9))
profileLabel.attributedText = myMutableString

참고 자료