When he works with limited color, his art is just as relaxed and confident.
One of Duvoisin's trademarks is his wonderful sense of humor---sophisicated, but loving. It shows up in much of what he produced.But, like so many illustrators, Duvoisin worked in many fields, not just children's books. As a young artist in Switzerland, he created scenery, textiles, and murals. In the US, he did a great deal of magazine work. Some of that art, such as this piece, is so different in style that we would not recognize it as coming from the same artist.
And some of the work that he did during WWII, for example, projects a dark and forbidding atmosphere, very different from his children's books.
There is not a great deal of information about Duvoisin on the internet. Two links will tell you a bit more about the author/artist: