Typically the black )or white/silver) on most razors is done through electro-chemical etching with the gold being applied gold leaf. Basically that is micro think metalic gold bonded to the steel with "sizing" (glue). A fine abrasive and a littlw work and the gold is gone. The black is more resilient and even when gone a ghost shadow of it may still appear as the metal itself is chemically changed where the etching was.

Tony