Blue Egyptian Eyes
To paint the blue of the eyes of the nymph (but also the sky and the sea in the background), Raffaello Sanzio had developed a unique experiment by recreating the famous “Egyptian blue”, the first artificial colour in history, whose use was lost after the end of the Roman Empire, replaced by lapis lazuli.
Raphael, The Triumph of Galatea, c. 1514, fresco, Villa Farnesina, Rome