If your camshafts are scratched like so it turned silverish what kind of problems can this cause and also is this extremely bad and need to be replaced?

 

it depends if the lobes are out of spec you will need to find the wear specs for your engine and then mesure them acordingly with a micrometer.
also used cam will have a polished look to the lobes but if they are within spec i wouldent wory about it.