@tomas Most of the main manufacturers do an “Indigo” but they are usually a blend to achieve that colour. The original indigo is a plant dye — as used for blue jeans. I quite like the Winsor & Newton Indigo — in fact, I picked the name because I happened to have a tube of it next to me when I was signing up for ADN and needed to pick a user name. I only bought the “Indigo genuine” later, just to play.