I had the same problem with the center caps on my 2000 Tundra.  The
dealer's parts people didn't have a clue but one of the service
writers said they have a guy who refurbishes the center caps and all
he does is sand and paint them.  He suggested I go to Pep Boys or Auto
Zone and look for the correct color.

At Pep Boys I found some silver spray paint, Dupli Color, High
Performance Wheel Coating that looked like a perfect match.  There is
no color number but the cap shows the color.  I've done all 4 of mine
and they look better than new.

I feathered where the paint had flaked away with some light emery
paper and washed all the dirt and dust off.  I found that 4-5 light
coats of the spray paint, with 10 minutes between coats, worked the
best.  The light coats prevents bubbling, pooling and running.  

Good luck

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