With Sonic, go to the place where you played chaos 0. 
Find a rock that looks like a chao egg then go into the 
antique shop. Go in the window and find a gold (looks 
green) and pick it up and put the rock where the gold 
one was (if you dont put the rock there than you will 
not get to get out of the store.) Take that to a chao 
garden and hatch it a gold chao will come out.
Go to the Mystic Ruins after you have done the above and 
press the button on the wall by the lake. A silver chao 
egg will fall out, let it float to shore then take it to 
a chao garden and you will have a silver chao (you will 
still have the other chao (gold)).