Freight Train by Donald Crews. I use the rainbow in class a lot. I think it is a really great tool for color recognition, sequencing, math, color theory and so much more. We used these vehicle counters and the children spent a lot of time at our sorting center. The felt pieces also made an appearance at our felt board. Train pieces were drawn by the mister and cut out by me. They match the colors and cars in Freight Train.
Other Train books we read:
Locomotive by Brian Floca
The Little Red Caboose by Marian Potter
Trains by Gail Gibbons
Chugga Chugga Choo Choo by Kevin Lewis
I Love Trains by Philemon Sturgess