Blue had no theatrical experience when he came to the screen. His first movie was The Birth of a Nation (1915), in which he was a stuntman and an extra. Next, he played another small part in Intolerance (1916). He also was a stuntman or stand-in for Sir Herbert Beerbohm Tree during the making of Macbeth (1916). Gradually moving to supporting roles for both D. W. Griffith and Cecil B. DeMille, Blue earned his breakthrough role as Danton in Orphans of the Storm, starring sisters Lillian and Dorothy Gish. Then, he rose to stardom as a rugged romantic lead along with top leading actresses such as Clara Bow, Gloria Swanson, and Norma Shearer. He was most often partnered with Marie Prevost, with whom he made several films in the mid-1920s at Warner Bros. Blue's finest silent-screen performance was as the alcoholic Doctor who finds paradise in MGM's White Shadows in the South Seas (1928). Blue became one of the few silent stars to survive the talkie revolution; however, he lost his Investments in the stock market crash of 1929.