Best way to take care of that is to buy rivets at the hardware store and automotive touch-up paint that is tan in color. Have been using that method for several years and looks great
If by "tan" you mean the ivory or off white rivets like those in my '85, it isn't worth worrying about. I bought regular white aluminum rivets, and even at close range I can't tell them from the ivory factory ones.
If they are really tan, or brown, they will need to be painted, as noted above.
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