Confidence: I'm as sure as I can be.
Notes: See ranon.2011's comment below. There are 3 common green nettle species. P. pomaceus has black legs and large spurs on the femora, is larger, a different colour green, and the green is often rubbed off. P. roboretanus and P. virideaeris are smaller with yellow legs, have no spurs on the femora and are a yellower green which is more resistant to getting rubbed off. P. roboretanus has very few green scales on the underside of the abdomen, whereas in fresh P. viridearis the green scales more or less cover the abdominal segements below. P. viridicollis occurs on a variety of herbaceous plants (including nettle), but isn't really green at all, except perhaps on the sides of the thorax. I'm guessing the vernacular name has got transferred from the similar sounding P. virideaeris.