Jan, I'd wait a bit to see if any growing buds show on the damaged stems, and if they do, cut back to the growing buds. If no buds do show, cut back to the ground, and the plants should regrow from the base.
How interesting! Thanks very much for the picture. Perhaps originally the yellow was grafted on a pink understock, and gradually the understock has sprouted more - it's probably more vigorous, too.