first of all i would point out for posting in the wrong forum,
now ur question,
it's true that when u play a chord all the strings ring together,u ask which one to identify...
ans: u don't have to..
play a C chord then an A chord, feel some difference??
this is what u have to get used to,
it will come eventually.. when u continue to play a variety of chords u'll start noticing the different tones..
but it will take a lot of practice.....
and don't stress on remembering the tone of a chord,
just listen attentively..
Now the most important thing,
make it a habit to use standard tuning every time u play,
by standard tuning i mean ,u shud use a tuner to do that
try it out, i'll post sum tips shortly.