How to set AlertDialog button font color in Kotlin

I know to setup font color in Java of AlertDialog button we can do like

dialog.setOnShowListener( new OnShowListener() {
    @Override
    public void onShow(DialogInterface arg0) {
        dialog.getButton(AlertDialog.BUTTON_NEGATIVE).setTextColor(COLOR_I_WANT);
    }
});

It unclear how to do it in Kotlin's style?

val alert = AlertDialog.Builder(activity)
var editTextAge: EditText? = null
with(alert) {
    setTitle("Settings")
    setMessage("Some text")
    setPositiveButton("OK") { dialog, whichButton ->
    dialog.dismiss()
    dialogMain.apply {
       activity.setupDialogStuff(view, this) {
                             //....
      }
   }
   setNegativeButton("NO") { dialog, whichButton ->
       dialog.dismiss()
                // set color of this button???
            }
        }
val dialog = alert.create()
dialog.setView(editTextAge)
dialog.show()