You need to rethink.

Many doctors will tell you how useful some colouring-in books were to them.

Here's one example, but there are others: https://www.amazon.co.uk/Human-Brain-Coloring-Book-Concepts/...

Richard Feynman said that if you wanted to quickly learn a subject you'd start with the books for children to get a quick overview.

It's a long running tradition, especially in medical education.

Here's an edition from 17 years ago: https://www.amazon.co.uk/Human-Brain-Coloring-Book-Concepts/...