For those of you who are familiar with Cafe des Iles, will it stain a translucent piston-filler? I love the color (based on the numerous examples I found on this site), but I am wondering if it is a saturated shade (despite it being by Herbin), or if it contains a lot of red, such that I should avoid it in my vintage translucent piston-filllers.

It's not an ink known for its saturation (quite the opposite), but red dye is red dye at any strength... Personally, I'd be hesitant to use it in a vintage pen.