The most recent version which I used this year in our Immunology course is actually yellow. It's the updated 2006-20007 version. Overall, the book is very complete and detailed. The diagrams are wonderful and just by flipping through the book, you can tell that it's very high quality. Also, the book is well-written and it's evident that Abbas is a master of immunology. After all, he was added as a co-author to the most recent edition (7th) of Robbins. In conjunction with this book, I also used the Lange Review of Microbiology and Immunology which is a much more CONCISE book and doesn't require as much reading per topic. Lange also has many questions to do at the end of the book which is quite useful in your studies. As Lange's title implies, it's a REVIEW, while Abbas's book is much more complete with regard to immunology. Good luck.
Edit: The newest version is actually the 3rd edition and has an orange and purple cover. Sorry for the confusion-on Amazon, it states that it was recently released. Anyways, my comments still pertain to the edition I have (2nd edition updated).