Rated 4 out of 5 stars

In combination with Personas or Themes, the following is useful to change the color of your bookmarks sidebar and bookmarks
Edite your userChrome.css by adding

@namespace url("http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul");
/* only needed once */ #bookmarks-view treechildren
{background-color:rgb(222,218,210) !important}

The 222,218,210 is something you can change depending upon what color you want as a background to your bookmarks.

See, www.tayloredmktg.com/rgb which has a chart of different colors with their three numbers (rgb code).

Using in FF4 Rated 4 out of 5 stars

I have been using AnyColor in FF4, but you need to disable the compatibility check
or use the Nightly Tester Tools add-on and use the option there to Force Addon Capatibility. The only issue then that I have found is that every time you start Firefox, in addition to your home page, you get a welcome to Anycolor in another tab.