A dark turquoise
I believe this ink was created for the Kensington (England) Pen Club or Show. Nonetheless, I purchased the sample bottle on a whim, and am really glad I did. It's a shade or two darker than standard turquoise, which I find much too light for daily use. It looks good on paper; easy to read, not hard on the eyes. Behaves well on multiple paper grades and in multiple pens. I have not been disappointed. I have probably 30 different blues and this is easily in the top 5.