Since Goku changed into a Super Saiyan in chapter 317 of the Dragon Ball Z manga and episode 95 of the anime fans of the Dragon Ball franchise have enjoyed watching these black-haired warriors turn into blondes. Why do they become blonde though? Editor in chief of Weekly Jump, Hiroyuki Nakano recently provided an explanation on Japanese TV.
According to Nakano, creator Akira Toriyama: “wanted to eliminate the time spent coloring in black [hair].” The original manga is black and white, so by not coloring in the black hair, it was left white. This, in turn, was translated as a blonde when it was colored. Wanting to trim time was due to the fact that it was a weekly issued manga and anytime they could save in coloring in hair could then be used for writing story or drawing other art.