I've decided to add my two pence as well!
I love "boring" inks!
Firstly, this is subjective and tastes differ very much. I've never found inks, which are described as "boring", to be boring or lacking in character. They have sheen, shading or can be plain uniform, which I also love.
Secondly, there is no real "secondly", as I lost my train of thought but still know what I wanted to write!
I started off with more "exciting" ink, which I've always loved, even when I was in school, like turquoises (eg Pelikan's, also Diamine Steel Blue) and even though I still have young eyes which see well and are not offended by brighter inks, it is undeniable that more muted and darker inks make for easier reading and don't depend as much on lighting conditions or mood (no one's always in the mood for bright colours).
I ditched those exciting inks fairly quickly and though I still like them, I never use them anymore. I like the idea of them more than the reality.
Diamine Asa Blue, Kensington Blue, J Herbin Eclat de Saphir, Sailor Nioi Sumire, Pelikan Topaz... is as exciting as it gets these days.
"Boring" inks also tend to fit any occasion, as I've recently added mentally as my own category: Appropriate for weddings and funerals.
Absolute favourites (apt for weddings & funerals) include these days: J Herbin Bleu des Profondeurs, Sailor Blue (& the very expensive Yonaga), Diamine Oxford Blue, Pilot Blue Black.
A daily carry in one of these colours will imo never be out of place.
(I also like Pilot & Sailor Black, JH Perle Noire and Waterman Serenity Blue, Parker Quink Blue, but I think those blues are less uniformly "fine" than darker blues, which strike a nice balance between being "business appropriate" and "interesting" if you so will).
Outside of the traditional writing colours (blue & black) I have no real use for any other colour and when I do, I use other pens. Any other colour would far sooner dry in a pen of mine than ever be used up, so buying bottles of these other colours would be wasted money, as much as it is exciting to be able to buy inks in so many colours, in my case it's useless.
I'm all here for the "boring" inks, which are anything but!