soap became a detergent in 1907 when a German company put the product "Persil" on the market. In addition to the carboxylic acid soap, "Persil" contained sodium perborate, sodium silicate and sodium carbonate. Hence perborate + silicate = "PERSIL".
http://www.chemistry.co.nz/introduction.htm
It could burn green but the sodium salts will burn yellow. I honestly don't know the answer, but if you have some, why not burn it and let people know what you observe? I, for one, would be interested to hear.