"Mr. Blue" is a song by DeWayne Blackwell that became a hit for the American vocal group, The Fleetwoods in 1959.
The backing track came from this YouTube video: https://youtu.be/NA50qCgFIKM?si=hfWj93JFzFUKAHRZ
This song's cover art is an oil on canvas painting titled "Nocturne: Blue and Silver - Chelsea" by American artist James Abbott McNeill Whistler in 1871.