The term grey literature was first used in the 1970s by British librarians in reference to information not found through regular book sellers (Auger, 1998, p. 3). These materials were labelled as "grey" in keeping with colour coding of other British documents, such as white papers for official documents printed on white paper and blue books for official reports printed with blue covers.
Grey literature refers to materials produced outside traditional publishing and distribution channels. It is not controlled, vetted, or reviewed by commercial publishers. It does not go through a peer review process. It includes research not intended for publication in academic journals or in book format. Grey literature is produced by many different groups including organizations, governments, and NGOs. Depending on what you are researching, consider the scope of grey literature and how it can inform your ideas.
Today, when information is referred to as "grey," the term may have negative connotations, implying that content is not trustworthy or accurate. This general association with sub-par material is not correct, but each source must be evaluated carefully. Refer to the C.R.I.T.I.C.A.L guide for a list of evaluation criteria that unpacks ways of thinking about information, especially through a lens of diversity and inclusion. Grey sources can lead to alternate and missing voices from the standard academic literature and are important to all fields of research.
Auger, C. P. (Charles P. (1998). Information sources in grey literature (4th ed.). Bowker-Saur.