My guess would be male, but it will be easier to tell when full grown. The females have more color usually, darker body, and a white stripe in their dorsal.
It looks like it's in the 2nd phase of its color change as a sub-adult. If it's a male, then it may take a bit longer (and at a longer length) for the full on dark green color to appear. Females will have a pink belly with the dark green and a white line in the dorsal fin. Since females are generally smaller, they tend to reach their adult coloration sooner and at less length than the males.