The UK academic networking community was one of the earliest to attempt to devise a complete set of open systems interconnection (OSI) standards for all aspects of its networking requirements, and to make a concerted effort to apply these to the entire community. A main thrust of the approach was the definition of protocols for each of the major networking requirements, each protocol being issued in a different coloured binder. The important protocols were:

• Yellow Book defining a transport service, roughly equivalent to layer 4 of the ISO seven-layer reference model.

• Green Book defining a terminal connection protocol.

• Blue Book defining a file transfer protocol.

• Grey Book defining an electronic mail service.

• Red Book defining a job transfer and submission protocol.

• Pink Book defining a transport service to run over an ISO OSI CSMA/CD service.

• Orange Book defining a network service running over a Cambridge Ring.

Colours have been used to identify various other standards, including CD-ROM format standards.