fix sidebar colors in html documentation

fix sidebar colors in html documentation

Change the default color of the TOC sidebar when no manual-specific color has been specified. Because the text color was changed to white, the TOC was not legible in manuals like the glossary, which is not assigned a color currently.

Also, darkened most of the manual TOC sidebars to separate from header and footer colors. Lightened the header and footer for the Contributor's Guide since it is the "black book."