ancient grey sweatophile
When I worked one, a Waterman, pen had Waterman red. The other, a Pelikan, had Pelikan blue black. In retirement it is just blue black.
This is such a great ink. Not only an exceptional performer, but the shading and colour change as you write is bewitching.
The trap I keep falling into of late, is inking up pens with something that isn't dissimilar enough, to something else I already have inked, so I don't get enough contrast on the page when switching pens.
I like to have enough difference between my inked-up pens to make sure there's a noticeable difference between them ... so I can make one note with one, then a second note with another on the same page, and easily tell the difference later on.
I find that nib size can add distinction between otherwise similar inks.