He is best known for his design of iconic stations constructed on the London Underground railway system in central London during the first decade of the 20th century, with distinctive oxblood red faïence blocks including pillars and semi-circular first-floor windows, and patterned tiled interiors done in the Modern Style (British Art Nouveau style).

[1] Green established his own practice as an architect in 1897, working initially from his father's offices, before moving to Haymarket in 1900 and then to Adelphi House on Adam Street, by the Strand, in 1903.

The exterior elevations were clad in non-loadbearing ox-blood red (sang de boeuf) glazed terracotta (faïence) blocks, provided by the Burmantofts Pottery.

The ground floor was divided into wide bays by columns, allowing separate entrances and exits, and also providing space for retail outlets.

The design also featured large semi-circular windows at first floor level (occasionally with circular oculi) and a heavy dentilated cornice above.

The station buildings were constructed with flat roofs with the deliberate aim of encouraging commercial office development above, another benefit of the load-bearing structural steel frame.

[1] Many of Green's station buildings survive, although internal modifications have seen most of his ticket hall designs altered to suit later developments.