Soylent Green was a food ingredient used in season 4, 30% Iron Chef. It is a type of food which Bender Bending Rodríguez and Elzar use in the competition. It is a reference to the 1973 film "Soylent Green." According to the dystopian film, Soylent Green is a wafer bar made from human remains in an effort to feed the population of a polluted and overcrowded planet.
The usage of the word "blue" is an inside joke at the unusual and sometimes illogical nuances of the Japanese language. In Japan, when someone is stopped by lit traffic signals but has not realised that it had changed to green (Midori), one would alert the driver by saying that it is blue (Ao).
Soylent green also appeared in an episode of The Simpsons.