John Malveaux: General Manager Sir Rudolph Bing opened the Metropolitan Opera's artistic roster to include singers of color, including Leontyne Price in 1955

John Malveaux of MusicUNTOLD.com writes:

Austrian born Sir Rudolf Bing (opera impresario) served as General Manager of the Metropolitan Opera from 1950-1972. He guided the Met move to a new home in Lincoln Center. After Leontyne Price historic Sept 16, 1966 opening as Cleopatra in Antony and Cleopatra, Op. 40 (opera in three acts) by American composer Samuel Barber at the new Met, other significant achievements of Bing's tenure included the opening the Met's artistic roster to singers of color such as Reri Grist, Grace Bumbry, Shirley Verrett, Martina Arroyo, George Shirley, Robert McFerrin, and others.  

Please see video of Leontyne Price https://www.youtube.com/watch?v=5kfOVNbhK3s Photo: Singer Leontyne Price (center) signs a contract with Metropolitan Opera representative Rudolf Bing (right). She was the first black performer to sing leading roles for the Met. Her manager, Sol Hurok (left), looks on, 1954. Courtesy: CSU Archives/Everett Collection