I don't have reliable information about a specific work titled "The Olive Trees of the Riviera" by Samuel Colman in the etching medium. While Samuel Colman (1832–1920) was an accomplished American landscape painter and etcher known for his Orientalist and Mediterranean scenes, I cannot verify the details of this particular artwork without risking inaccuracy. I'd recommend consulting museum collections, the Smithsonian American Art Museum, or specialized print catalogues for authoritative information about this work.