“Is it open access?” sounds like a yes-or-no question, but open access is not one thing. It is a set of distinct routes — conventionally labelled by colour — that differ in who pays, what licence applies, where the work lives, and, crucially, who is included or excluded by the economics. Those differences are not technicalities: they determine whether open access widens participation in scholarship or quietly reproduces existing inequities. That is why the routes belong in the knowledge-equity domain. For the plain-language starting point, see What is open access?
First, what open access actually means
True open access is more than “free to read”. It means a work is freely available online and carries reuse rights, normally via a Creative Commons licence — most often CC BY. The reuse rights are the part people forget: a paywalled article temporarily made free, or a PDF posted with all rights reserved, is free-to-read but not openly licensed, and so not fully open access. Holding that distinction in mind is what makes the colour scheme legible, because the colours differ precisely on the licence-and-venue axis.
The two foundational routes
Green open access — self-archiving
Green open access is achieved by the author depositing a version of the manuscript in a repository — an institutional repository or a subject repository — making it freely accessible independently of the publisher’s paywall. Typically the deposited version is the accepted manuscript (the peer-reviewed, pre-typeset version), and access is sometimes subject to a publisher embargo before it can be made public. Green’s great virtue is that it costs the author nothing and works alongside any journal: the article can appear in a subscription journal while a green copy sits openly in a repository. Its limitation is that the openly available version may not be the formatted version of record, and embargoes delay access.
Gold open access — open at the publisher
Gold open access means the version of record is made openly available immediately at the publisher, under an open licence, on the journal’s own site. The question gold raises is who pays for it. In many gold journals the cost is recovered through an Article Processing Charge (APC) — a fee, often substantial, charged to the author or their funder. This is where the equity problem bites: an APC-funded gold model can simply move the barrier from the reader to the author, excluding researchers without grants or institutional funds, and bearing hardest on those in lower-income settings. APC waivers exist to mitigate this, but they are a patch on a model whose default is pay-to-publish.
Diamond: open with no charge to anyone
Diamond (or platinum) open access is the model that breaks the pay-to-publish bind: the version of record is openly available immediately, under an open licence, with no charge to authors or readers. Costs are met by the community — typically through institutional, library, scholarly-society, or public funding of the publishing infrastructure itself, rather than per-article fees. Diamond is the model most aligned with knowledge equity, because it removes the barrier at both ends: nobody pays to read, and nobody pays to publish. Much of it operates outside the large commercial publishers, and a substantial share of the world’s diamond journals are run by scholarly communities and supported by regional infrastructures — the Latin American platforms SciELO, Redalyc, Latindex, and the AmeliCA initiative being prominent examples of community-owned, fee-free publishing at scale. Diamond’s challenge is sustainability: it depends on continued collective funding rather than a per-article revenue stream.
The other colours, briefly
- Bronze — free to read on the publisher’s site but without an open licence. The publisher can withdraw access at any time, and reuse rights are absent. Bronze is free-to-read, not genuinely open.
- Hybrid — a subscription journal that offers individual articles as gold (usually for an APC) while the rest of the journal stays behind a paywall. Hybrid is widely criticised for “double dipping”, where institutions pay both subscriptions and APCs.
- Black — articles obtained through unauthorised channels. This is not a publishing model and not a route an author chooses; it is mentioned only because the term circulates.
How Plan S reshaped the landscape
The policy backdrop to all of this is Plan S, the initiative led by the funder coalition cOAlition S, which requires that research it funds be made openly available immediately, with no embargo, under an open licence (CC BY by default). Plan S deliberately accepts multiple compliant routes — gold in a fully open-access journal, green via immediate repository deposit under a rights-retention strategy, or publication in a diamond venue — while explicitly disfavouring hybrid as a long-term destination. Its mechanism for the transition was the transformative agreement, a deal between institutions and publishers (often called read-and-publish) intended to convert subscription spend into open-access publishing and shift journals toward full openness over a defined period. Whether transformative agreements are a bridge to a fully open future or a way of entrenching incumbent publishers’ revenues is one of the live debates in the field.
Choosing a route
- Check your funder’s requirements first. If you are bound by Plan S or a similar policy, the compliant routes — immediate gold, compliant green, or diamond — are defined for you, and an embargoed green copy may not satisfy them.
- Prefer routes that do not price out colleagues. Where a strong diamond venue exists for your field, it is the most equitable choice. Where gold is the route, check for fee waivers.
- Always secure an open licence, not just free-to-read. A CC BY (or funder-mandated) licence is what makes the work genuinely open and reusable.
- Use green to complement, not as an afterthought. Even when you publish gold or diamond, depositing in your institutional repository improves discoverability and preservation.
Where shared vocabulary fits
“Open access”, “gold”, “green”, “diamond”, “APC”, and “transformative agreement” are used inconsistently across funders, publishers, and institutions, which makes a single open-access policy hard to apply across systems. A shared, federated vocabulary that defines these routes precisely — pointing back to cOAlition S for Plan S and to the recognised open-access definitions — is what lets a policy written for one context be understood in another. Supplying that definitional layer is the role the CASRAI dictionary is designed to play; the relevant terms sit in the knowledge-equity domain.
