Chrysoine resorcinol is a synthetic azo dye which was formerly used as a food additive.  In Europe, it was banned as a food additive in 1977. In the US, it was banned in 1988.
Chrysoine resorcinol can be used as a pH indicator with a color change between pH 11 and pH 12.7.
In colorimetry, it has an absorption maximum of 387 nm.