While teaching, I would have the kids find a friend to do this art activity. I would paint one child's hand blue and one child's hand yellow. Then they squished their hands together representing the hug in the book.
Since I only have one child, we adapted it this way to make a book.
One hand was painted one color the other hand painted a different color, then rug together.
We made hand prints on paper I had printed simple words to recreate the story.
"This is Little Red. This is Little Blue. They are friends. They hugged, and hugged, and hugged. They turned Purple.
We did all the primary colors and added white to red and black.
My daughter loves singing the mixing colors song on Little fingers that play.