Back in the mid to late 70s I recall a wonderful picture book that I read at primary school. I cannot remember any title or author details, but I do remember that the book was perhaps set in a forest? The illustrations were black and white until the last page I think, where they became full colour. I think they were line drawings. I imagine the book was published in the early 70s, maybe late 60s. I remember something about a rainbow as part of the story, i think this is why it was full colour on the last page. I also think a child was moving through the book. Thanks for your help