Diamine Kelly Green is a vivid, bright green with distinctly yellow undertones. For me, this means that in light strokes or fine nibbed pens, the color is in that “sweet spot” of lime, citrus-y green that I love so much. For someone else, it could mean a bright green that has gone decidedly off.
In my Noodler’s Ahab fountain pen with the flex nib, there was a lot of shading in the writing. Some might think too much shading as the top, lightest part of the strokes is a very light yellow-green while the down strokes are a clover green. It makes readability a bit iffy.
With a regular stiff nib, the ink is much lighter overall. More Kool-Aid Limeade green than a true Kelly green.
I quite like the color that results from using this ink with a fine or medium nib as it goes decidedly lime. However, if you are looking for a bold true green, this will not be the one for you.