UCSF Web Standards and Policies

It is common for web editors and administrators not to know the standards and guidelines for building UCSF websites. Very few people have website building as their primary job responsibility. 

UC Policy on electronic accessibility.

You will want to make sure your site meets the AA  standard for accessibility

UCSF Identity guidelines

The http://identity.ucsf.edu website gives the design standards for building UCSF websites.
Part of the reason the color palette for the web starter kit seems limited is that it complies with the accessibility policy and the identity guidelines.

Can I use other Themes?

Sure, as long as they meet the AA  standard for accessibility and UCSF identity guidelines.

Can I use any of the Themes I see on the UCSF Shared root?

No, some of the themes are there for troubleshooting. For example, the Garland theme is a basic part of the Drupal installation. It's sometimes used to troubleshoot problems with the other themes. That’s why it's still available even though it doesn't meet UCSF identity guidelines...