Acid blue 9,is a synthetic organic compound used primarily as a blue colorant for processed foods, medications, dietary supplements, and cosmetics. It is classified as a triarylmethane dye and is known under various names, such as FD&C Blue No. 1 .
Acid blue 9, has been used as a coloring dye to determine the feeding behaviour in Drosophila. It has been used as a coloring dye for determining the number of egg masses of Meloidogyne incognita