Buying a Green Papaya: You can try looking for a very green papaya at your grocery store (either 2 Hawaiian or 1 Caribbean type). But personally, I recommend buying one at an Asian store (as pictured), simply because it is difficult to tell whether a papaya is green or actually in one of the stages of ripening.
Asian stores and markets sell green papayas labelled as such. Sometimes they are even sliced open so you can see it is green inside (the seeds will be white).


