IMO The only thing a painted head does is add to the profile of a lure - making it appear a bit larger to a fish. Looking up, a fish sees the entire shape of a lure, but looking sideways or down, it sees the material used (silicone, soft plastic, hair, etc.) minus an unpainted jig head. If the head is painted, whatever the color, it is included in overall profile and/or brightness of a lure.
A black jig head with a black skirt may or may not get more strikes, but when I fish for smallmouth, I want a black head when using black soft plastic lures or skirted jigs with trailers. A confidence thing I suppose after catching river fish on that combination. Same thing for LM - black head / black skirt and swimbaits - I prefer a head the same color as the lure - usually in a pearl color, if only to extend the perceived visual length and shape
of the lure.
(Note: fluorescent jig head colors are IMO a distraction from the body of the lure unless the lure's color is also fluorescent.
As for small finesse soft plastics, hair or feather jigs, unpainted are preferred so as to keep the fish's focus on the lure's action which may be enhanced by it's color while at the same time making the lure appear as small as I want it to be. Lure action when it comes to the three materials mentioned is crucial and far outweighs jig head color especially when using clear plastic grubs: