[aab0]

They (I believe, although it might be the other guys) have a video up on YouTube demonstrating it on a Vietnam movie trailer. It looks appalling: aside from the usual averaged colors and saturation, the coloring is highly unstable and changes from second to second.

[MelmanGI]

Thank you for the hint!

Found a video [1] colorized with the approach by these guys with the unstable coloring.

There are some other videos [2][3] colorized using differing approaches, that don't seem to have as much color unstability though the color in general appears more off.

Could of course also just be a property of the underlying source.

[1] https://www.youtube.com/watch?v=__kcHbzSNC4 [2] https://www.youtube.com/watch?v=_MJU8VK2PI4 [3] https://www.youtube.com/watch?v=qQSViqdd0tU

[Kequc]

It seems like adding the colour would be the hard part. Once you had that, normalising the colour or smoothing it out across hundreds of similar images could be achieved by a second software algorithm.

Certainly colour correction, hue, contrast, brightness, would be easier to process than adding colour in the first place.