OK, a bit of geeky viticultural stuff.
I’d always been told that Portuguese variety Sousao was a teinturier: a grape with coloured flesh. Normally red grapes have all their pigment in the skins and the flesh is transparent. With teinturier varieties, of which there are very few, the flesh is also coloured. They make incredibly dark coloured wines.
Sousao also makes dark coloured wines. Also known as Vinhao (in Vinho Verde), it’s an interesting variety, but I can confirm from first hand experience it isn’t a teinturier. It just has highly pigmented skins that give up their colour easily.
Pictured here are Sousao and Alicante Bouschet (the most famous teinturier variety, grown widely in the Alentejo and southern France). You can see the difference.