This is the Stream Glory, a species of Damselfly, (Neurobasis chinensis), often seen as a flash of brilliant green around streams in Hong Kong.
The aptly named Stream Glory have one set of clear and one set of "solid" wings, which look oh so beautiful when they fly, or when displayed to attract a mate. To take this picture I headed to a river near Bride's Pool where I had seen them previously, and took a couple of hours while my wife Sally sketched. The sky was overcast, even some rain, so low light. Old (12+ years, no IS) 70-200mm zoom handheld, BUT multiple frame per second Canon 1DXMkII body.
I found the little critter, and as i could not take "in-flight" pics due to the low light, after observation I found that the moment after he landed he flashed his solid wings, once, maybe twice for a split second before folding his wings again. In these pics the wings are in rapid movement. The images are also heavily (80%) cropped. I used lightroom for selective NR (noise reduction) and also some luminance adjustment (which gets rid of some grain, but blurs the details). All these pics were shot around ISO 1250 1/320s f6.3-8
Here the male is flashing his wings.
Males have very iridescent green hindwings which are flashed in display to attract females. The colour is produced by interference from the thin surfaces of the wing membrane. Female is very similar to the male. But its wings are transparent and light coffee brown with white wings spots.