The blue/green staining indicates constant high pH in the pool and importantly will not harm the operation of the copper rods. It is important to monitor your pH at least once a week to fortnight and keep the levels within range of 7.2-7.6 and the stains will eventually disappear.
To clean the stains off the rods simply turn the system OFF, remove the rods and mix 1 part hydrochloric acid to 10 parts of water in a bucket and place them in the solution for 10 -15 mins or until the stains have been removed.
If blue/green staining has occurred within the cell housing, simply turn off the unit and remove both the cell and ioniser and clean it with fresh water and a mild household cleanser ensuring to rinse it out once completed.