Hi Sas,
I thought Portuguese knew their colors better than UC-DAVIS :) LOL ... And thought the dark to be the Preto.
But since Preto is in a pot, the comparison is not that fair. Perhaps she gets less sun too, and that would explain the lighter skin.
Since Black Madeira is a late ripening cultivar and she is in the ground, it is surprising to see her ripen fruits at this time of the year.
Have you tried the Preto in ground ?