I was in Tokyo recently and bought a ton of Iroshizuku inks: I love their properties and their colours, they're sold everywhere in Tokyo, and they're amazingly cheap, so I bought eleven bottles.
The more I used Shin-Ryoku, forest green, though, the less interesting I found it. It's still an attractive colour, but it's kind of dull in the long run. So I did the obvious thing: I made a mix, 2 parts Shin-Ryoku to 3 parts Chiku-Rin, light yellow-green. For my purposes, the mix is better than either: fresh and bright but still dark enough to be readable. The name "wakakusa" means "young grass".
(Please excuse the spotty scan: the scanner is nearing the end of its useful life, I think.)