Maybe it depends on the type of guitar? The Beatles had Epiphone Casinos in the mid 60's, on which John and George sanded off the finish. George said that once they’d removed the finish, they became much better guitars. “I think that works on a lot of guitars,” he explained. “If you take the paint and varnish off and get the bare wood, it seems to sort of breathe.” Of course, those Casinos are acoustic instruments, to an extent, not solid body, no center block. So there's that. They did change the color, by scraping it off to the bare wood, though this may be more about finish than color. Anyway they felt it made a difference, and they were pretty savvy about music. For what that's worth. 