Machine-learning techniques for automated colorization are increasingly effective and accessible. I came across a Python library by Algorithmia that makes colorization very easy. If you have a working installation of Python, all you need to do is install the package and get an API key. Then just a few a few lines of code will colorize any image.
So I naturally started searching my mind for black and white photos I've never seen colorized, of interesting people who lived before the advent of widespread color photography. Europe gets a bad rap nowadays, but I've always had a soft spot for twentieth-century European political radicalism — thinkers and actors. Narrowing my focus to this domain, I did some searching for high-resolution black-and-white photos of exemplary figures, which have never been seen in color before.
The colorization model works impressively well right out of the box. I made no tweaks to the default options. One can spot a couple of weird shadings here and there, but all of the colorized photos below look very natural and plausible in my opinion. There were a few duds I excluded, but they were mostly due to low-resolution in the original photograph, I think.
The most beautiful colorization here is the 1949 photo of Simone De Beauvoir, below. The one that's most surprising or incongruous is the one of Gilles Deleuze and Claire Parnet, also below: while the original black-and-white lends them some mystery and gravitas, the colorized version makes them look like a family-friendly department store advertisement.
The colorization of Andreas Baader in late 1960s Berlin is perhaps the one that adds the most vibrancy and cultural context. It's well known that many of the left-wing terrorist movements of the late twentieth century trafficked in hipster aesthetics, but my mental images of left-wing terrorist fashion revolve mostly around leather jackets and other black-chic garments. Little did I know that Baader wore the same kind of thick red lumberjack shirt that many leftist hipsters wear today! I can't tell if Baader's shirt is flanel or perhaps polyester, which was probably in, or coming in, at the time? I have no idea what's going on with his eyes though; he's either been beat up or it's a problem with the original image. The original black-and-white is a negative from the Berlin police archive — I think those are police trailing him — so that might explain it.