Green: Self-archived of the pre- or post-print of articles in repositories.
Gold: Under a Creative Commons (or similar license), the article is fully accessible on the journal website. An Article Publishing Charge (APC) is usually paid.
Hybrid: While the journal may be access-restricted by the publisher, the authors are able to purchase their articles with an APC that allows them to be open access.
Bronze: The articles are freely accessible on publisher's servers, but do not have the clear details on reuse.
Diamond: Publication is free of charge for both readers and authors. In other words, it's the Gold model without any APCs.
Black: Illegal Open Access. Sharing of content without any authorizations or permissions.