Scheele’s Green was a deadly color
Scheele’s Green was invented in 1775 by Carl Wilhelm Scheele. The pigment was originally prepared by making a solution of sodium carbonate. The temperature of the sodium carbonate was about 90 °C. Slowly adding arsenious oxide, this mixed was constantly stirred until everything had dissolved. This produced a sodium arsenite solution. In the 19th century, the toxicity of arsenic compounds was not readily known.
A Fashionable Trend
19th-century journals reported of children wasting away in bright green rooms. Many others were dying, for example, ladies in green dresses swooning and newspaper printers being overcome by arsenic vapors. There is one example of acute poisoning of children attending a Christmas party where dyed candles were burned.
During Napoleon’s exile in St. Helena, he resided in a very luxurious room painted bright green, his favorite color. Consequently, his cause of death is generally believed to be stomach cancer, and arsenic exposure has been linked to an increased risk of gastric carcinoma. 1960s Tests on Napoleon’s hair samples revealed high amounts of arsenic which has been linked to higher rates of cancer in humans.
The beautiful green pigment was used to color almost everything: household products, artificial flowers, clothing, children’s toys, and even as a food dye in sweets. The pigment brought with it burns, rashes, illness, and death by arsenic poisoning.
There are many reasons
more info here: History of Scheel’s green