Length ~5mm. A blue-green species, the first antennal segment is pale above with a dark line on the underside.

Other green Mirid bugs. 

Photos showing key features required. Dissection of male left clasper helps with confirmation. 

On a range of deciduous trees, including Oak, Lime and Ash. 

Summer-Autumn. 

Widespread in Britain.

Rarely recorded in Leicestershire and Rutland.

https://www.britishbugs.org.uk/heteroptera/Miridae/orthotylus_nassatus.html