An excellent approximation of the genuine indigo pigment, available here.
This is almost black in masstone when mixed with white it gives wonderful, almost cerulean tints of cold blue. The tints have an almost flat feel in look (in a good way!).
There is a slight green undertone, probably from the Phthalo blue pigment in it's makeup.
Lovely quality, no fillers or additives.
Technical Overview
Pigment - PB29 , PB15, PBk7, PBk9
Binder - Single Estate Cold Pressed Linseed Oil
Opacity - Semi-Transparent
Drying Time - Medium