Color contrast (length: 8:26) from the Online Content Accessibility Workshop: 

This course is designed for those responsible for creating and maintaining content for online-based instruction and the web. It is suitable for both technical and non-technical audiences. In this 3-hour workshop (over two days, 1.5 hours per session), you will learn why accessibility matters, an overview of various standards and legal requirements, the tools available to test your content for accessibility and core principles to produce accessible content. The concepts and principles are relevant for both document accessibility and online-only formats.