Hi Frank - found some helpful info for you. Hope this helps you out.
Porsche wheel colors and codes with date of launch
Diamantsilber Met. 1992. 61M
Stahalgrau Met Matt. 1997. 61W
Felgensilber Met. 1997. 9A1
AluSatiniert 03 Met Matt. 2003. 4W9
Orange. 2006. 8C6. M2
Rallyeschwarz Mat. 2005. L03C
Some people recommend using Wurth Silber
Helpful thread:
https://rennlist.com/forums/993-forum/573618-wheel-paint-success.html?referrerid=18268