One by Kathryn Otoshi

Blue is a quiet color. Red’s a hothead who likes to pick on Blue. Yellow, Orange, Green, and Purple don’t like what they see, but what can they do? When no one speaks up, things get out of hand — until One comes along and shows all the colors how to stand up, stand together, and count. As budding young readers learn about numbers, counting, and primary and secondary colors, they also learn about accepting each other's differences and how it sometimes just takes one voice to make everyone count.

I really enjoyed this book. The illustrations are deceptively simple for such a complex issues as bullying, self-confidence and making right choices. I especially liked the consistent use of the colour in the text. It allows for additional conversations with the kids reading it, enabling them to evaluate what is happening, make predictions and become involved in the story rather than just reading it.
A beautiful book, the illustrations of the number one demonstrate how standing up and speaking up can make you feel tall and strong. The physicality of the colours express how each is feeling much better than words can, making the emotions of the story more accessible for the class. It also allows for great follow-up activities where students can draw their own pictures to show how they feel now or in various situations. "One" provides a common visual language to discuss emotions and a manner in which to share those feelings with classmates.

Here is a book trailer for the book:

Book trailer for One: