> I wonder how much this kind of depiction was an artefact of animation/video production in a black-and-white or early-colour era

Zero. Nada, Nothing.

The history of blackface begins with stage and musical performances "aping" actual black musicians and banjo players [1].

There wasn't a lot of film work happening in 1848 . . .

[1] https://en.wikipedia.org/wiki/Minstrel_show