A long time ago, I created a script that would parse a CSS file and generate the unwritten style guide that's embodied in it. Until I resurrect that script, you might need to refer to other helpful resources on creating a Style Guide
Really Simple Example
This is a navline, or header with background-color:#212121
Heading color #2c2c2c
This is paragraph text in #464946. Links within the text are colored rgb(6, 51, 96) or #063360, and decorated for email
This is darker text in #333333