Change custom text field background color and text color IOS Swift

Add self as a target for the UIControl events you need according to documentation

There you have control events for EditingDidBegin and such.

Something like this:

self.addTarget(self, action: "myFunc", forControlEvents: UIControlEvents.EditingDidBegin);

Select the text field -> click "identity inspector" icon -> click on Plus button "user Defined runtime attributes" -> add this text "_placeholderLabel.textColor" in "key path" field -> choose the "Type" "color" and set the value color.

In your CustomTextField class you can add a property observer:

var change: Bool = false {
    didSet {
        textColor = change ? .yellow : .black
        backgroundColor = change ? .blue : .white
    }
}

and in your ViewController:

func textFieldDidBeginEditing(textField: UITextField) {
    customTextField.change = true
}

func textFieldDidEndEditing(textField: UITextField) {
    customTextField.change = false
}

Don't forget to set the delegate of your textfield, in storyboard or programmatically.

EDIT:
Shortened the code and updated for Swift 3