Hisoku

The color of the finest celadon. It is a pale blue-green with a mysterious hue. Celadon was made during the Tang dynasty at the Yue kilns in Yuezhou, China, by coating the entire piece with a pale blue glaze containing iron. Because celadon was presented to the emperor, the color of celadon became a forbidden color and apparently came to be called hisoku (secret color).