Don José Moñino y Redondo, Conde de Floridablanca Pompeo Girolamo Batoni (1708-1787)

The picture has something of this: people, portrait, wear, man, music, veil, costume, opera, monarch, gold, leader, crown, royalty, theater, outfit.
Perhaps it’s a painting of a man in a red coat holding a piece of paper in his right hand and a book in his left hand.