I ate at the western buffet in Sanya Hotel, Hainan. Especially sour meatballs are dark green and white, like pickles, used to mix salads.

The dark green one should be watermelon willow. Watermelon willow, also known as watermelon button, water-hung pomegranate and sour bean, is a green shrub of roses, which is native to the Mediterranean coast and Spain. Its fruit is sour and astringent and can be used for seasoning. At present, most products on the market are bottled pickled products. Watermelon willow is often used for appetizers such as steak tartar, seafood dishes, cold sauce and salad.

The white one may be pearl onion (also called chicken tail onion). . . Not sure. . .