Pop colours: Ring with octagon. Brand: Thomas Sabo. Ring with a three-dimensional octagon. Octagon is hand-painted with cold enamel in a pastel shade of green. Green octagon-cut stone is the ring's radiant centrepiece. Richly detailed design with fine engraved lines. Gently rounded ring shank for superior comfort. 925 Sterling silver, cold enamel/ glass-ceramic stone. Thomas Sabo Charming Pop Octagonal Green Stone Ring.