Lo kao (descibed as a greenish indigo) was a true novelty hit in the 1850´s. Until then, the main green dyes were composed of a mixture of yellow and blue dyes. Imperfect mixing led to unstable and not very lightfast colours. Lo kao dyed green without mixing. Before the discovery of its source plants the dye quickly became extremely expensive (the magazine Volksvlijt mentions a price of Dfl. 250 for a pound in 1854). After some experimentation Natalis Rondot found out that the dye was actually decocted from the bark of two related Rhamnus (buckthorn) species, R. utilis and R.chlorophorus. There are several books and articles that demonstrate the intense interest that the discovery caused, starting with Rondot's own Notice du vert de Chine (1858), followed by numerous articles in scientific magazines. A German publication, simply titled Das Chinagrün by Karl Löffler, surfaced in 1861.
A good overview of the research of the French into Chinese silk and its dyeing (and the subsequential interest of the Chinese in French sericulture) is online here: link
It proved a short-lived craze, however. Chemists made a slightly inferior buch much cheaper alternative from the European buckthorn, which, in its turn, was replaced in the 1860's by synthetic rapidly dyeing greens.