Noodler's Gruene Cactus is neither a light green or a dark green. It's a bright, mid-spectrum shade. I'd call it a kelly green, but different people have different concepts of color names. The scan is close, but not perfect. The lightest variations here are a little lighter than the written sample and the darkest areas shown are showing a wee bit darker.

IIRC, this ink didn't rapidly turn darker in pens. As I mentioned above, I can't use it on many of the papers I'd like to, due to smearing it with my left hand, so I haven't had it loaded for any length of time for quite some time & can't say for sure if it is 2 weeks, for example, before it before it turns darker in pens...But I can say that my notes don't indicate that this was a problem.
For my own use, I've made a half n' half mix of Pelikan 4001 Green & Herbin Vert Pre with a tad of Sheaffer yellow to closely replicate the color. But for folks that don't have a left hand smearing problem I think this pretty ink deserves the review.
Best, Ann