The pedestrian crossing signals in London’s Trafalgar Square are fitted with a variety of different green lights, such as can be seen in the two examples in the photograph. I have not seen these sorts of green signals anywhere else in London. They are a part of a project to promote ‘diversity’ in London.

For more detail, see: https://www.london.gov.uk/press-releases/mayoral/diversity-pedestrian-traffic-signals#:~:text=Around%2050%20pedestrian%20traffic%20signals,new%20’holding%20hands’%20design)