Its the dispassionate search for the Indigo Blue color which is the origin of this collection of Japanese designs of nineteenth century. Sun Blue,Circles, Crossing, Flower Pale Blue and Polygonium.
Polygonium tinctorium the medicinal plant which you use to dye fabric of this special Blue.
(Read more: http://www.wildcolours.co.uk/html/j_indigo_dye.html)
The designs are from the Japan Blue Collection.