Pilot Iroshizuku Shin-Ryoku fountain pen ink is a dark green ink inspired by the forest.
Chiku-rin is a blue-green green that's appears strong and striking. If you're a watercolour user, you can think of this ink as Phthalo Green.
This ink has a good contrast against paper.
For writing and drawing purposes, this ink performs well. There's an attractive sheen, a gradation of colour, to the strokes.
Below are direct links to the ink on Amazon.