Those are AUX inputs. A different-colored (black, here) collar around a jack is normally an output; jacks without that are generally inputs. Except here, for some weird reason. Annoying.
-- Lugia
Hi Lugia,
I was also trying to find some standard in this however there isn't really. I came across a few modules (different brands but I forgot which were the clear examples here, might be indeed Intellijel is one of them) that are just a contradiction to what we are trying to find here ;-)
And then there are those brands that just have one background front panel colour, so they don't either way, some obvious examples are Doepfer, Erica Synths, etcetera.
So, for myself, I would rather not rely on it. Just my 2 cents. Kind regards, Garfield.
For review reports of Eurorack modules, please refer to https://garfieldmodular.net/ for PDF formatted downloads