Is this true ?

[Soppa Saia People]

Is the fact that Toriyama handpicked Nozawa as Goku's voice actor ? I've always assumed it was always a common knowledge thing that everyone knew about but I'm starting to have doubts and I can't find any (credible) interviews.

[FlorianGran]

From the Daizenshuu 3 interview

— Were there any jobs you did directly for the “DB” anime?
Toriyama: In cases where characters appeared in the anime before they were shown in color in the manga, I sent a response to the animators at Toei through my editor. After that, I listened to the voice actor audition tapes, and decided on the casting. When I decided on Goku’s voice, I listened to the voices of five or six candidates, and out of those I decided on Masako Nozawa-san.

— What were your impressions on hearing Goku’s voice during the actual broadcast?
Toriyama: I went “Goku has this sort of voice, doesn’t he”. From then on, when I was drawing the manga, the characters’ voices would somehow drift up into my mind. Whenever that happened, Goku’s voice would be just like Nozawa-san‘s, and I’d think “Geez, she’s good”. Now it’s impossible to separate Goku from Nozawa-san.

— Did you choose any of the other characters?
Toriyama: I was present for the selection of the other major roles. After that, I suppose I only designated Mayumi Tanaka-san as the voice of Kuririn. When I saw “Night on the Galaxy Railroad”, I said the protagonist had a really good voice, and a very knowledgeable friend of mine told me that it was Mayumi Tanaka-san.

[Gyt Kaliba]

— Were there any jobs you did directly for the “DB” anime?
Toriyama: In cases where characters appeared in the anime before they were shown in color in the manga, I sent a response to the animators at Toei through my editor. After that, I listened to the voice actor audition tapes, and decided on the casting. When I decided on Goku’s voice, I listened to the voices of five or six candidates, and out of those I decided on Masako Nozawa-san.

Huh. First time I've heard specifically the bolded part, or at least thought about it. Do we have any indication at what point in time he started to do that? I'm curious now as to whether Bulma's hair color change was actually a mistake, or something Toriyama said 'you know, she might look better this way' about and either kept it consistent in the manga or just later changed his mind about it again.

[TheBlackPaladin]

I assume that they've been lost and/or destroyed by now, but man, how cool would it be to listen to those audition tapes? Not just to hear the voices of Goku that could have been, but also to hear Nozawa's first attempt at what would become her most famous character? I love behind-the-scenes stuff, so that would be quite the cool find.

[Polyphase Avatron]

So is that why Vegeta's hair was red in his first appearance in the anime, because he hadn't been drawn in color yet? And Toriyama sent a letter to complain about it?

[Gyt Kaliba]

I assume that they've been lost and/or destroyed by now, but man, how cool would it be to listen to those audition tapes? Not just to hear the voices of Goku that could have been, but also to hear Nozawa's first attempt at what would become her most famous character? I love behind-the-scenes stuff, so that would be quite the cool find.

Oh man, that would be amazing to hear. I'd be curious to hear what other actors auditioned for major parts in the series over the years period. Heck, I'd love to hear Tanaka do her best take on Goku, given Luffy and all, and likewise have Nozawa do her best take on Kuririn.

[VegettoEX]

So is that why Vegeta's hair was red in his first appearance in the anime, because he hadn't been drawn in color yet? And Toriyama sent a letter to complain about it?

Well, I wouldn't get too far ahead of ourselves. It's also just as likely that Toei used that color, no-one said anything, Toriyama used other colors when he did a color chapter, and Toei said "Oh crap oh OK let's do that." We don't know for sure just how long into production Toriyama was still actively reviewing week-to-week materials on that nitty-gritty a basis (let's be honest: probably not long at all). That particular quote seems like he's referencing the VERY BEGINNING of the series.