What did Johnny mean when e told pony boy to stay gold?

What Johnny Cade was trying to tell Ponyboy (in the letter Ponyboy found in his copy of "Gone with the Wind", because Johnny never actually physically recited it) was that everyone changes, for the better or for the worst. Johnny told Ponyboy to stay gold because he knew Ponyboy was different than the other gang members and that he was under a lot of pressure from it. Staying gold meant, in a way, to stay yourself.

Not totally sure about the answer....you can find the exact meaning at the end of the book.