I've been rewriting the Eureka media browser and I've added support for High Contrast themes via the new CSS Properties. CSS Properties make integrating high contrast support into styles much easier, and also allow end users to customize the look and feel with very little knowledge of the CSS structure.
The themes use the high contrast media queries to automatically switched on based on the user agent (operating system preferences). There's screenshots, docs, and links to a demo here:
I intend to submit a DRAFT to the MODX Advisory Board that would ensure that the next all-new MODX Manager (4.0) uses similar patterns for high contrast support.