how Cu(ii) ions differ from Zn(ii) and Mg (ii) as regarding their reaction with sodium hydroxide and ammonia?

( The color is only one minor but important detail. The most important observation is how those different ions react with the same reagents such as NaOH and NH3. Why is it important? If you have a sample of water which contains two out of the three ions, you will be able to determine which ions it contains by reacting the sample of water with NaOH and NH3. Magnesium ion and Zinc will precipitated upon addition of one drop of the NaOH solution. How do you know which one is which? NH3 will also react differently with with the three ions producing different results (precipitation, color).)