Victor, as far as I know, all 68 side marker bezels were painted black inside the grooves. I've never seen any with white or had no paint in them*, but this isn't something I've done a lot of research on.
However, if you go by the AIM, under Z22 there's no note for this on the non illustrated parts page (Z22 page A2), and nothing in the rest of that UPC section showing anything different, so I would say with the evidence of the AIM and the P&A, there was only one set of bezels used, 3925429 for the fronts and 3927459 for the rears.
* I would imagine that after 40 some odd years of cleanings, especially using tooth picks and tooth brushes, some of the black in the grooves would be scrubbed off, but there should be some reminents of black in the corners. Mine are almost clean (no paint), but I DO show bits of black in several areas.