The OAK (Open Access to Knowledge) Law Project has published A Review and Analysis of Academic Publishing Agreements and Open Access Policies.
Here's an excerpt from the "Conclusion and Next Steps":
The review of publishers’ open access policies and practices found that:
- the majority of publishers did not have a formal open access policy;
- only four of the total sample of 64 publishers surveyed had a formal open access policy;
- 62.5% of the publishers were able to provide sufficient information to enable them to be “colour classified” using the SHERPA/RoMEO colour classification system to denote levels of open access;
- using the SHERPA/RoMEO colour classifications:
- 25% of the surveyed publishers were “green” (permitting archiving of the pre-print and post-print versions of published articles);
- 4.7% were “blue” (permitting archiving of the post-print version);
- 6.25% were “yellow” (permitting archiving of the pre-print version);
- 26.6% were “white” (archiving not formally supported).