UILabel with text of two different colors

My answer has also the option to color all the occurrence of a text not only one occurrence of it : "wa ba wa ba dubdub" , you can color all the occurrence of wa not only the first occurrence like the accepted answer.

extension NSMutableAttributedString{
    func setColorForText(_ textToFind: String, with color: UIColor) {
        let range = self.mutableString.range(of: textToFind, options: .caseInsensitive)
        if range.location != NSNotFound {
            addAttribute(NSForegroundColorAttributeName, value: color, range: range)
        }
    }

    func setColorForAllOccuranceOfText(_ textToFind: String, with color: UIColor) {
        let inputLength = self.string.count
        let searchLength = textToFind.count
        var range = NSRange(location: 0, length: self.length)

        while (range.location != NSNotFound) {
            range = (self.string as NSString).range(of: textToFind, options: [], range: range)
            if (range.location != NSNotFound) {
                self.addAttribute(NSForegroundColorAttributeName, value: color, range: NSRange(location: range.location, length: searchLength))
                range = NSRange(location: range.location + range.length, length: inputLength - (range.location + range.length))
            }
        }
    }
}

Now you can do this :

let message = NSMutableAttributedString(string: "wa ba wa ba dubdub")
message.setColorForText(subtitle, with: UIColor.red) 
// or the below one if you want all the occurrence to be colored 
message.setColorForAllOccuranceOfText("wa", with: UIColor.red) 
// then you set this attributed string to your label :
lblMessage.attributedText = message

There is a Swift 3.0 solution

extension UILabel{


    func setSubTextColor(pSubString : String, pColor : UIColor){
        let attributedString: NSMutableAttributedString = NSMutableAttributedString(string: self.text!);
        let range = attributedString.mutableString.range(of: pSubString, options:NSString.CompareOptions.caseInsensitive)
        if range.location != NSNotFound {
            attributedString.addAttribute(NSForegroundColorAttributeName, value: pColor, range: range);
        }
        self.attributedText = attributedString

    }
}

And there is an example of call :

let colorString = " (string in red)"
self.mLabel.text = "classic color" + colorString
self.mLabel.setSubTextColor(pSubString: colorString, pColor: UIColor.red)

In my case I'm using Xcode 10.1. There is a option of switching between plain text and Attributed text in Label text in Interface Builder

Hope this may help someone else..!

extension UILabel{

    func setSubTextColor(pSubString : String, pColor : UIColor){


        let attributedString: NSMutableAttributedString = self.attributedText != nil ? NSMutableAttributedString(attributedString: self.attributedText!) : NSMutableAttributedString(string: self.text!);


        let range = attributedString.mutableString.range(of: pSubString, options:NSString.CompareOptions.caseInsensitive)
        if range.location != NSNotFound {
            attributedString.addAttribute(NSForegroundColorAttributeName, value: pColor, range: range);
        }
        self.attributedText = attributedString

    }
}

SwiftRichString works perfect! You can use + to concatenate two attributed string