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 Jiff or something similar ensuring to rinse it out once completed.