No, the army would fly the liege's banner, or the king's, depending on who owned their fealty. But the army would be most likely to have the liege's banner as an insigina on their shields, and to fly his colors, and there would be at least one king's banner to acknowledge that the liege owed his fealty to the king. Unless of course they were fighting the king

Talent is God's gift to you. Using it is your gift to God.