The first time I saw green-centered guava was from a distance. It was at the bottom of a metro station in Taipei which the locals call jie yun. Amidst of the hustle and bustle, a guy hunched over a pile of green fruits, concentrating on carving out the core of one with a knife. He cut the halves into bite-size cubes and sealed a bunch in a zip log bag, and laid it out on his tiny cart to sell. The August heat was like a damp cloth sticking on me. The fresh green of the fruits looked deliciously cool.
Later, I saw them again in the morning market. I asked what they are called and how to eat them.
Ba le is their Chinese name. And they are indeed deliciously cool.
I read there are other variations, including one with the same skin color but pink center. They have lots of fiber. Because they are only slightly sweet, people say they are ideal for diabetic people.
Without further due, let me introduce a gift of nature.
like coffee, like tea 
Such a beautiful presentation of fruit! They should go to art books!