Comment 8 for bug 27867

There should be TWO checkboxes in the color setting preferences, NOT one. One should set whether to use your background and text colors. The second should set whether to use your link colors. This may be the checking to see if main reason that this is not working properly now. It is NOT doing what you say it will do in the Help file entry:
 "Colors Dialog:

Text and Background

        Here you can change the default text and background color to be used on
        web pages that haven't specified that information. Click on the color
        samples to select colors.

Use system colors

        Check this optionpreference to use the colors defined in your OS settings
        instead of the colors specified above.

Link Colors

      Here you can change the default colors for Web links. Click on the color
        samples to select colors.

Underline links

        By default, links are underlined on web pages. Uncheck this optionpreference
        to disable this. Note that many sites specify their own styling rules
        and this optionpreference has no effect on those sites.

Allow pages to choose their own colors, instead of my selections
        above

        By default, Firefox uses the colors specified by the web page
        author. Disabling this optionpreference will force all sites to use your
        default colors instead."

Please take Special NOTE of the last Paragraph of the Help file entry! Having only ONE checkbox makes it impossible for users to choose anything other than page default underlining without some type of work-around. This is especially annoying on pages where they make the visited links the same color as unvisited links, so please make it possible to select these two color customizations independently so that we can customize our links without killing site colors for backgrounds and text. This is the root of this bug!