The Consultative Committee for Space Data Systems (known as CCSDS) has many publications describing the design, development and use of data systems in the space domain. These books are categorised into a range of colours, which have deeper meaning than just trying to look appealing.
Key books
Blue: Recommended Standard. Effectively these are the “CCSDS Standards” you hear referred to. They present detailed requirements that must be met in order to be compliant with the standard. Some may have various optional parts but discussion and rationale is usually kept to a minimum.
Green: Informative Report. These documents are not standards in the same way the blue books are; rather they provide additional description, flavour and rationale for the standard, process or approach they discuss.
Magenta: Recommended Practice. Similar to the Blue books but with a focus on process or approaches. These don’t tend to be quite as formally written as blue books, and do not usually contain the same rigidity of requirements.
Other books
Other documents are used to manage drafts and updates to the documents above.
Red books are drafts of the Blue and Magenta books described above, and should be used with caution!
Pink books (or Pink sheets) are updates to existing documents, and are used to review updates before formal release.
Orange books are experimental, that is although they may have formal requirements in them, the contents have yet to obtain enough consensus by agencies to fully standardise them. As with red books, these should be used with care.