青釉 is the iron-bearing glaze that gives celadon (
青瓷) its trademark green-grey hue, fired in reducing atmosphere. Famous variants:
粉青 fěnqīng 'powder green' and
梅子青 méiziqīng 'plum green' from the Longquan kilns
龙泉窑 (Zhejiang) at their Southern Song peak.