swift NSMutableAttributedString text color

extension NSMutableAttributedString {

    

    static public func multicolorTextAttribute(fullText : String, colorText : String, fontColor : UIColor, label : UILabel) -> NSMutableAttributedString {

        

        var mutableString = NSMutableAttributedString()

        

        let range = fullText.rangeOfString(colorText)

        let index: Int = fullText.startIndex.distanceTo(range!.startIndex)

        mutableString = NSMutableAttributedString(string: fullText as String, attributes: [NSFontAttributeName:label.font])

        

        mutableString.addAttribute(NSForegroundColorAttributeName, value: fontColor, range: NSRange(location:index,length:colorText.characters.count))

        

        return mutableString

    }

    

}