The funny thing is he has been kind of attacked on Twitter recently for bizarre reasons ... people are pointing out how colorization detracts from the source material, or ruins history, etc.
What this really is, is a hacker making the world's best neural net in the world at a certain task. (It appears to have also become his day job now.)
Let's try to appreciate what an achievement it really is. Pretty much all of the automatic colorization you may have seen online in the last year is some version of DeOldify.