It's just a variant of kale, part of the genus _Brassica_. I think you'd call this particular variant redbor or purple, bluntly, but you could go further because kale is often classified by the type of leaf. So in your picture, curly 'redbor' or 'purple' kale.
This is your specific name: _Brassica oleracea_ Acephala Group.
(just sort of look at wikipedia)