I have about 15 inked up pens on my desk as we speak. I have then in various glass trays along with their corresponding inks so it is pretty easy to keep them straight. Moreover, my default ink is often the "synced" to the brand of pen as are the colors of the pens themselves i.e.
Blue Lamy Al-Star= blue Lamy ink
Grey Lamy Al-Star= black Lamy ink
Silver Parker 45-Parker Blue ink
Silver Parker 45
w/ black end cap= Parker Blank Ink
Silver Parker 45
w/gold end cap= Parker Blue/Black ink
Blue Pilot Metropolitan...
Black Pilot Metropolitan...
Blue Lamy Al-Star= blue Lamy ink
Grey Lamy Al-Star= black Lamy ink
Silver Parker 45-Parker Blue ink
Silver Parker 45
w/ black end cap= Parker Blank Ink
Silver Parker 45
w/gold end cap= Parker Blue/Black ink
Blue Pilot Metropolitan...
Black Pilot Metropolitan...