The hormone used to degreen citrus fruits is

The hormone used to degreen citrus fruits is Ethylene.
Degreening is the process of removing the green colouring (known as chlorophyll) from the skin of citrus fruit.
The ethylene degreening treatment of citrus fruit does not improve consumption quality; on the contrary, it contributes to physiological disorders, senescence and loss from decay such as Diplodia stem-end rot and anthracnose.