Green kerosene in copper container goes colorless
The brass is a metal mixture of cooper and zinc. Copper compounds are known to form blue and green salts.

Examples: Copper Chloride



I believe that green color it's a copper compound and the copper reacted with oxygen (air) and the preciptate is copper oxide. 



Also, the oxygen solubility in hidrocarbons it's around 60/70 ppm¹.
¹Corrosion for everybody - Alec Groissman