Open access (OA) mandates are policies that require researchers to provide free, unrestricted access to their published research by including it in OA journals (gold OA) or depositing it in freely available disciplinary or institutional repositories (green OA). This study measures the degree of compliance with a Spanish government OA mandate 2.5 years after its implementation. A total of 58.4% of articles resulting from publicly funded research had at least one OA copy available 1 year after publication. Among these, 23.8% were in gold OA, 21.8% in green OA and 12.8% in gray OA, i.e., posted on websites and social networks. Most of the green OA articles were in 2 disciplinary repositories: arXiv and PubMed Central. Just 14.4% of the articles resulting from publicly funded research were available in institutional repositories, although more than 90% of the articles in the data set were the result of projects carried out at institutions that have such an archive. There is great potential for growth in green OA, because over two thirds of the articles that were not available as OA were published in journals whose publishers allow a preprint or a postprint copy to be deposited.