I thought so far that silver is chosen because of a hair changing color with age.
I'm of the understanding that you hit silver first, then you are golden. It is the same for anniversaries, isn't it? 25 years of marriage is silver and 50 is gold?
I don't think there is any connection with silver and golden anniversaries.
Referring to old people with "silver" probably refers to the hair, "golden years" I guess is because of relaxing in retirement and the wisdom of old age.