A medium-small damselfly. The thick blue stripe on its thorax can distinguish it from other blue damselflies. The other common and similar damselfly, the Azure, has a much thinner stripe. With a little practice, picking out this difference in the field is relatively easy. Mature females have three colour forms: ‘blue’, ‘brown’ (which is often yellowish-orange) and typical (greenish).
The males are a drab pink/purple when just emerged, taking a few days to become blue.
However they can be distinguished from females by having solid blue on the bottom 2 abdominal segments.