I love a really dark lacquer paint for book shelves. This black looks so chic and navy is a great option, as well.
I realize these are not built-ins, but I loved the color of the shelves and the cool picture as a focal point.
I love the floor to ceiling bookshelf behind a couch. This is a similar layout to our living room and it makes me want to make our book shelf take up the entire wall! I am also in a major green mood so this green velvet curtain with the pops of pink is definitely speaking to me!