'Nightlife' is not a registered peony and is likely an existing registered plant for which the label has been lost (or ignored) and has been given a commercial or trade name - something I really do not like and that causes further confusion. Because of this, I would not expect a reputable vendor to carry this and I would not recommend purchasing it. I suspect the color of this photo has been manipulated. It would be difficult to find this colour tone in natural lighting in a herbaceous peony cultivar. If you are seeking out this colour in peonies, I would take a look at the woody peony 'Pluto'.
