It is a nice picture, but unfortunately it is hard to see anything distinctive. There are many small Lasioglossum species that are frequently found on Wahlenbergia and one of the most abundant is L. cognatum. If we could see yellow on the lower face then we could say it was a male Lasioglossum. If the colour of the thorax is genuinely greenish, then it would probably be L. cognatum. As it is, we can only say that it might be.
Thank you @michael.batley for your help. I'm posting another photo of the same bee, same flower. I'm not sure it will give you any more information to positively ID though.