Typically, open access publications and repositories use a color taxonomy to denote what path to open access is available, but this is not descriptive, so it can be confusing what each of them mean. Here is a brief list of the most common types:
- Gold Open Access: Traditionally published journal articles that are available for anyone to access and read. Typically, these are funded by Article Processing Charges (APCs) paid by the author or author's institution in lieu of subscription fees.
- Green Open Access: Repository-based open access. Many institutions have their own repository, but there are subject-specific repositories and preprint repositories that house green OA content as well. Typically, these will include preprints (submitted version of articles) and/or postprints (or author's accepted manuscript, AAM; reviewed and corrected version of articles that do not include publisher typesetting or formatting). If your article is published in a journal, you may or may not be permitted to archive your work in a green open access repository immediately; check with your publisher to see if there is an embargo.
- Hybrid Open Access: Refers to a journal that contains both open access and closed access articles. Note that in these cases, the publisher is collecting fees both from APCs to publish the open access articles and subscription fees to access the others.
- Diamond Open Access: These are journals that are available for anyone to access and read, but they do not collect APCs or any other kind of fee from authors. These journals are often university-based, and they may receive funding from the university, grants, or philanthropic organizations in order to operate.
- Bronze Open Access: This is a less common distinction; bronze open access content is openly available for all to read online, but it does not have (or it is unclear whether it has) persistent access guarantees in place or clear sharing and reuse guidelines. In other words, it could just disappear at any time without warning.
