I think there are additional factors mentioned in the article. Apart from the black/white aspect of printing (though the covers had colour): > Off went Young

I think there are additional factors mentioned in the article. Apart from the black/white aspect of printing (though the covers had colour): > Off went Young to the London Zoo, where the “fiercely modernist” Penguin Pond exhibit had opened the year before to general acclaim. As the article pointed out, Penguin started with a bit of left bias, and modernism (and futurism) were associated with and inspirational to the left as they embodied change, as opposed to the conservative stance of the right. While that has nothing to do with the animals themselves (who tend, like all animals, to be pretty conservative) one can imagine how, when visiting such an exhibition, the architechture could establish a philosophical penumbra for Young, especially given the times we're talking about.