While all forms of open access fall broadly into either the green or gold classification, there are additional, nuanced, forms of open access which are used to highlight distinguishing features among the varieties. Because these terms are also often used to describe open access, it is worth understanding their unique features.
Platinum or Diamond Open Access
Platinum open access gets its name from its association with gold open access, as it is seen as a premier or superior form. The distinguishing characteristic of platinum open access is that articles are published open access immediately in open access journals but there are no article processing charges (APCs) back to the author. As discussed previously, APCs are a common characteristic of gold OA, yet it is not true that all or even most OA journals charge these fees. Many gold OA journals rely on institutional support, grants, memberships etc. to fund their publication and as a result do not ask their authors to contribute any additional funds. It is because these journals do not charge back any costs to authors that they are granted the platinum distinction.
Hybrid Open Access
Hybrid open access is used to describe a journal that publishes both gold open access and traditional subscription-based research. These journals present their authors with the choice to either pay an APC and have their work disseminated as open access, or to submit it as a non-OA article. Hybrid journals are a contentious issue among OA advocates, as they largely reinforce the supremacy of traditional publication venues and often provide an additional revenue stream to already profitable journals. Hybrid journals also tend to have substantial APC charges, with the more prestigious journals charging the highest fees. Notably, academic libraries take issue with hybrid journals as they charge authors to make a subsection of their articles open access, but still require libraries to pay undiscounted subscription fees to access the additional pay-walled content. As a result, hybrid journals are often accused of “double dipping”.
Bronze Open Access
Bronze open access refers to scholarship that may be publicly available online but does not include clear reuse permission. Because of this lack of clarity, bronze is used to confer its inferior status in relation to gold or platinum open access literature, which is clearly marked for reuse. Whether or not bronze open access meets funder requirements or other open access polices is dependent on individual polices. According to a 2018 study, Bronze OA, while little talked about may be the most prevalent form of OA in practice.