My thanks to Glenn for the ink sample.
Platinum Citrus Black is an iron gall ink and that means it’s waterproof. I found Citrus Black to be an incredibly dry ink. In my Platinum 3776 SM, it was so dry it squeaked as I write. Did a mouse died in my pen? Obviously not. Turns out my Platinum 3776 SM couldn’t handle it. Switching it to my Karas Kustoms Fountain K makes it way more readable. It goes down a dull yellow almost gold but after a while it darkens like all iron gall inks do. As it darkens it goes to a dark greenish-yellow. It’s an interesting colour for sure, it just needs the right pen to be paired with it.