This might be a stupid question but here it goes. If a guitar is finished in charcoal black/faded grey or any of the "black tinted" colors would it be at all possible to just sand it down a little bit and then apply another color tint as that is technically the same process that you would use on a clean top?
Or do you need to sand it all the way down and seal and start over?

What about the SE veneers? Would a bit of sanding on for example a brown quilt top make it possible to turn it grey/black?