Paper Girl did a very extensive review of the new Herbin Vert de Gris fountain pen ink.
This is one of the most thorough ink reviews I’ve ever seen! She did writing samples on several different types of paper (including but not limited to Rhodia, Leuchtturm, and two different weights of Tomoe River papers), and used various nibs. She tested drying times, feathering, show through, saturation, shading and sheen on the papers.
It was very interesting to see the same ink tested on different papers. I was surprised at the variation in crispness and shading of the ink.
She compares the color with other inks in her collection and was pleased to find it was unlike anything else she had. She describes the color:
The colour of Vert de Gris to my eye is more blue than green. Monitor display settings may make the colour look bluer than it actually is. On the page, the grey is just as prominent, if not more so. It’s hard to pin down. I would describe Vert de Gris as a complex, steely blue-grey with just a touch of green.