Confidence: It might be this.
Notes: I'm not sure this is a common blue. There's a clear 'spur' on the side of the thorax which would suggest not. Also, while S8 is coloured, S9 isn't and if it is a female, there's too much coluration on S8. The colour of the thorax is confusing as it looks like either VERY thick antehumeral stripes or a coloured back, but I think this may be a red herring. I think I detect black and white pterostigma, which would again suggest a blue tailed damsel rather than a common blue.