I just remembered that there is another style.css. Before I realized that you can edit php and css directly from the WordPress dashboard, I was doing it the hard way — accessing the files via ftp, and reuploading edited versions.
There is a style.css for the chocotheme, BUT there is also another style.css for the “darkgray” chocotheme option that I’m using.
To this “darkgray” style.css, I made the following edits:
#logo a { color: #6d4a24; }
#header .description { color: #6d4a24; }
So no more white text on a light background! Yay!