Astro Boy: Hero of Space
This is a compilation film released in 1964, based on three episodes of the Astro Boy TV series.
This edition is a full colourisation/restoration using AI-based restoration techniques, broadcast on NHK G on 2025-03-30. (somehow related to their celebrations of 100 years of broadcasting)
To be clear, this is an official release, with the restoration/AI stuff done by NHK and/or Tezuka Productions (it’s not clear exactly who). All I did was rip it.

Some more info here:
https://tezukaosamu.net/jp/mushi/entry/34518.html (japanese)
https://www.animenewsnetwork.com/news/2025-03-30/1964-astro-boy-hero-of-space-anime-film-fully-colorized-using-ai/.223041

An older release here:
https://nyaa.iss.one/view/535928 (presumably not colourised)

honestly i’m not sure the restoration is very good, I preferred the Original side of their comparison
but i enjoyed the film and the colours looked nice

世界歴２００４年。宇宙人に向けて通信メッセージを送るほどに科学を発達させた地球では、その英知の結晶である高性能ロボット・アトムが日夜活躍を続けていた。ある日、科学省は、多数の部品ロボットが合体して完成する“ロボット宇宙艇”を開発。人工島司令官・ベガ大佐の妨害にあうものの、アトムの活躍で事なきを得た。ところがその宇宙艇で月へ向かったお茶の水博士が、謎の怪物にさらわれてしまう。
In Japanese with CCs.