Possible Clues:

• Copper patina
• Diver's rig treated with bluish coating
• Green-blue deposit on copper
• Patina on copper
• Go back, Father, and dig the knight up till all is green
• It's up to the priest and the knight between them to do the spadework for the green
• Greenish blue coating on copper
• The cleric and the knight come up to get around to dig till all is green
• It's up to the priest to do the spadework to get the knight back for the green
• Green patina that forms on copper, brass and bronze — diver's rig (anag)