— indigo-blue , adj.
1. indigo (def. 4).
2. Also called indigo, indigotin . a dark-blue, water-insoluble, crystalline powder, C 16 H 10 N 2 O 2 , having a bronzelike luster, the essential coloring principle of which is contained along with other substances in the dye indigo and which can be produced synthetically.
[ 1705-15 ]