"The blue Cologne is an original variety that was already cultivated 5900 years ago at the foot of the Carpathian Mountains by Stone Age immigrants from northern China. 200 years ago the blue Cologne had its main distribution in the turning areas of historical Styria, in Slovenia, Croatia and on Istria. The Cologne was a variety for the medieval warm period. It should not have played a role in the Little Ice Age that followed. It is possible that he came into the Swabian Bilfinger collection as Scheuchner around 1750." (https://historische-rebsorten.de/rebsorte/blauer-koelner/)