“My premise was simply to identify a train and let it go,” explains author and illustrator Donald Crews. “I had to constantly fight against showing or saying more than that.”

It’s a good job, as Freight Train is a triumph of simplicity. Starting with an empty track, Crews introduces each carriage, one by one, moving progressively along the colour spectrum: a red guard’s van, an orange petrol tanker, a yellow grain hopper… However, what ensues is almost cinematic. The next page zooms out to show all the carriages together, headed up by a black engine, with steam billowing out across the white space of the page. Page by page, the train accelerates, going through tunnels, by cities and over bridges, the solid blocks of colour that make up its carriages blurring and merging together. There can be no simpler way of introducing children to the interaction between colours.

First published in 1978, as an introduction to colour, this classic remains unbeaten: subtlety didactic and pleasing to the eye of child and adult alike, it is a glorious celebration of all the most basic and most sophisticated uses of colour.

Illustrator Hailing from New Jersey, USA, Donald Crews has authored and illustrated a plethora of picturebooks, including the abstract alphabet classic We Read: A–Z, which he published after a brief spell in the US military in Germany. Transportation is a major theme of his work, with titles such as Flying, Sail Away, Schoolbus, Truck and Freight Train – for which he won the 1979 Caldecott Medal.