Michael Ende's DIE UNENDLICHE GESCHICHTE (THE NEVERENDING STORY) was one of my favourite novels when I was a child. Not only is the story magical, but also the book itself is beautifully made (or at least the edition I own was beautifully made). As you can see from these pictures, the book was printed in two colours: red for the real world and green for Fantastica.. There were also beautiful illustrations at the beginning of each chapter.
An amusing side note: I always thought Atréju had green skin. When I looked up his description a few months ago, I realised that he isn't really supposed to be green: he is described as olive-skinned. (But who cares? For the past thirty years, my Atréju has had green skin... *g*)