It's actually interesting seeing some of the guesses it makes. For instance:

https://youtu.be/qQSViqdd0tU?t=82

It makes a reasonable effort to distinguish skin from what it presumes is grass, but the grass looks mostly to just be rock. But even then, you can see it distinguish some of the bigger rocks from the rest of the ground in the back by how it colorizes the larger stones near the center of the frame.

Pretty neat. Goes without saying that accuracy might improve further if the neural net can be further trained on videos as opposed to stills (going by the description in the video where it's noted that the video is colorized frame by frame via http://richzhang.github.io/colorization/).

Unrelated: this film seems neat.