I'm not sure that my oil pan was painted (CB750K6-76). I have not seen clear coat either as the other covers.
Painted the oil pan when restoring the bike 2013, it had no traces at all of any paint. I had thoughts about corrosion protection.
I used same rattle can paint as I used on cases, cylinder and head. Motip, color alu.
The ongoing K2 build has a not painted pan right now. I'll paint one to be used at the oil change when I clear the oil pump strainer after rebuild.