Adding colour to black & white

Today there was a small article in the Observer about this technique of painting in colour:-

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I can see some merit in this if there is a wish to guess what the scene may have looked like in colour, before colour was available. But would not most originals have been taken in black & white on purpose in the first place, or am I missing something?

Most of the originals they show were taken on B&W because that was all that was available. Even the later ones from the depression, were in B&W because that's all the newspapers could use, and color was far to expensive and difficult to process and reproduce.
I think it's an interesting exercise, and there's nothing wrong with doing this so long as it's not misrepresented. If a different person did this, it would be different.

One of the ways they colorized images back then was to spray them with a type of retouching spray ( that adds tooth or grit) and then use pastels like a pastel artist. (which are like chalk sticks.)