One theme to rule them all...
A naming standards repository for using custom properties to theme the web.
These variables are extremely powerful when used with web components since most properties do not pierce the Shadow DOM, but custom properties do. Beyond just web components though, this idea of a theme layer can be valuable to bringing together code from disparate code bases, making them look and feel consistent across the page with minimal implementation effort. If we can come together on an agreed set of global variables, think of the savings we'll get too from printing one set of variables instead of having to print similar variables with prefixes for every type of component or system on your page.
To jump right in, checkout the wiki and the join us in discussions via the issue queue.