Lamy Dark Lilac. Along with my Dark Lilac Lamy Safari I ordered a box of cartridges of the accompanying ink. In the Safari with medium nib, Dark Lilac ink is a nice dark purple, fairly saturated, and without much shading. It really flows well, too.
Here is Dark Lilac ink compared to two purple inks I own and then to a standard blue ink and black ink for reference.
Dark Lilac is dark enough that you could possibly get away with it at work. Depending, of course, on how fabulous your work setting is, and on how cool, or near-sighted, your boss is.
It’s a Sign o’ the Times that this purple also makes me think of the recently departed Prince. Would the Purple One himself like this ink? Oh yeah: it totally reminds me of the cover of 1999.