Orange Book If you ever record a CD-ROM, you'll be using the Orange Book standard. It's the format that enables CD-R drives to record discs that regular CD-ROM players can read. The main difference between it and other formats, such as Red Book and Yellow Book, is that Orange Book defines how CD-R devices can append index data to an existing disc's directory if you add more data to the disc in multiple sessions. See also: CD-R, Yellow Book, Red Book