This is a scan of S. T. Dupont Royal Blue cartridges loaded in a Pelikan Future pen. This ink is so light that it is almost not visible on some papers. Looks like a washed out version of Dupont's Night Blue ink but with a more gray green tone.

I'm not sure if it's because you're using cartridges, but my bottle of Dupont Blue is darker than the way it appears on your scan. Interesting... I may have to use a Dupont Blue cartridge to see if there's any variation in colour. What is the size of the nib on the Pelikan Future pen? Perhaps that has something to do with the colour variation. I don't have a Pelikan Future, but I've noticed (which is quite common) that different nibs produce different colour variations of the same ink.

The pen has a Medium nib. I believe that the paper that I am using has much more to do with the shade than the nib. The three papers that I use the most are 1) Moleskine (used in my journal) 2) Ink jet compatible paper (used at home for general purpose) and 3) Xerox paper (universally used at work for nearly everything. I also do some writing on legal pads. The Dupont inks are quite light on all of these. However, when I "clear" my pens on blotting paper, the lines are as dark as the bottles would indicate. I was also writing some letters on Rossi stationary yesterday and noticed that the Dupont Night Blue wrote darker than my previous tests would indicate.