When & where did the unnatural hair color aka "You gotta have blue hair trope" originate?


I specifically want to know which manga or anime started the trend, so I can
reason from there to the how question, in order to not make general
assumptions.

There was a time in manga/anime where blue hair was abnormal. For example,
from the short clips I've seen of the anime "アタックNo.1", it contains mostly
black-haired girls, a couple of brunettes and a sparse blonde. No one there is
pink/red/blue-haired. Same with Princess Knight.




Urusei Yatsura had characters with weird hair colors as far back as 1981 and
is generally the originator of a lot of things that make anime anime.

But then three years earlier **Uchuu Kaizoku Captain Harlock (1978)** already
featured someone with a blue hair color.

That character was an alien, though.

[![Uchuu Kaizoku Captain
Harlock](https://i.stack.imgur.com/xemNem.jpg)](https://i.stack.imgur.com/xemNem.jpg)

Truth be told,... the characters with weird hair colors in Urusei Yatsura were
also all aliens.

Similarly, **Kidou Senshi Gundam 0079 (1979)** had characters with blue hair:

[![M'Quve](https://i.stack.imgur.com/4eD0G.png)](https://i.stack.imgur.com/4eD0G.png)
[![Lalah
Sune](https://files.catbox.moe/mx6pd0.webp)](https://files.catbox.moe/mx6pd0.webp)

Even earlier, **Majokko Meg-chan (1974)** :

[![enter image description
here](https://i.stack.imgur.com/o5UQb.jpg)](https://i.stack.imgur.com/o5UQb.jpg)
[![enter image description
here](https://i.stack.imgur.com/mScfl.jpg)](https://i.stack.imgur.com/mScfl.jpg)

And I guess the following could also be interesting in general:

[![enter image description
here](https://i.stack.imgur.com/1gPfi.jpg)](https://i.stack.imgur.com/1gPfi.jpg)

[![enter image description
here](https://i.stack.imgur.com/kQrKm.jpg)](https://i.stack.imgur.com/kQrKm.jpg)

