Differences between cable sound.

Posting for a friend just getting into 2 channel. He's buying a phono pre and I suggested getting a better interconnect. Since he's low on cash the suggestion was made to get some copper cables from Blue Jean for starters. Now he's starting to do some reading and came back with"I read that silver are so much better". I tried telling him not better but different. In general terms, what do you folks think is the difference between the sound of copper, silver and gold in interconnects?

Thanks, Boss302