Types of Open Access publishing

Gold

An author publishes their article in an Open Access journal that allows free access to articles immediately upon publication.

Learn more:
Directory of Open Access Journals
Evaluating journals
Cost Effectiveness for Open Access Journals

Green

Here the author first publishes their work in a journal of their choice, and then deposits, or "self-archives", a version of the work in either an institutional or subject repository, making it freely available. The version which can be deposited is specified by the publisher.

Learn more:
The NDSU Institutional Repository is an Open Access repository for works by NDSU faculty, staff, and students.
List of discipline-specific repositories.
The SHERPA/RoMEO database has publishers’ copyright policies regarding Open Access repositories.

Hybrid

Toll-access journals that allow authors to make their articles Open Access for a fee.