i think your question is only applicable when you have a car with matching numbers and all original with zero rust ... then it could make a difference in selling price. if you were doing a full restoration and you wanted to return a car to its original color and it was numbers matching, it might make a difference / it might not.
my 2800cs was originally baikal - previous owner painted it black ... it does not have the original engine. i am painting it the color i want (an e9 original color but not a 2800cs color) ... because i don't care about value / potential value as an original car ... because mine has a tranny change, a brake change, an engine change and an interior change. i will admit that even though i love ceylon, the original baikal keeps appearing in my mind that before they spray it (hopefully soon) that i should go original color.
to me, all original gets the highest value, restored / perfect condition gets close (even with changes)