The W21 wheels had silver painted non-chrome "faces" and only came in silver/light argent. These were the standard wheels on the 1970 Sport Fury GT on which the chrome version was optional. If your dad's S/23 had color matched wheels either the dealer painted them or your dad had them painted somewhere. It is possible, but very unlikely, that they were special ordered to be painted body color IMHO based on my 25+ years with C Body cars, during which I have never heard of nor have I seen in person or in photos body colored W21 wheels.