Diazodinitrophenol (DDNP) was one of the first diazonium or diazo compounds ever produced; it was subsequently used to make dyes and explosives. It forms yellow crystals in pure form; however, the color of impure forms may vary from dark yellow to green to dark brown.
The compounds of every Wikipedia article carrying a Chembox or a Drugbox, refreshed daily, with the values their infoboxes give. The pages need JavaScript; the API does not.