To achieve a perfect copper tone in the hair ideally you would need to take out most the previous colour. ...More >
You could do this in a number of ways.
use this shampoo for a month and it should hopefully lift enough for a good base for the copper colour.
milkshake lightning oil-
milkshake do a great product called lightning oil, NO ammonia and its not a bleach but it will lift coloured hair enough to make a PERFECT base
if none of these are an option, you CAN put a copper tone over previous colour but you would have to make sure it was similar dept to your hair colour now.
Hope this helps