how can I use custom css style in the default theme of trac?

I have some trouble with my trac installation (version 11.4). What should I do to change i.e. some colors in the default theme? I've found various tips in the net, but nothing worked yet as most tips were for the 10.x version.

Are there any options in trac.ini or should I add a special xyz.css somewhere in my environment?

Please help me, I don't like the default black & white design ;)

Solution

Instructions for how to do this for version 0.11 can be found at the Trac site, here's an example from that page that adds custom CSS as well as a header and a footer.

Say you want to add a link to a custom stylesheet, and then your own header and footer. Create a file /path/to/env/templates/site.html or /path/to/inherit/option/templates_dir/site.html, with contents like this:

<html xmlns="http://www.w3.org/1999/xhtml"
      xmlns:py="http://genshi.edgewall.org/"
      py:strip="">

  <!--! Add site-specific style sheet -->
  <head py:match="head" py:attrs="select('@*')">
    ${select('*')}
    <link rel="stylesheet" type="text/css"
          href="${href.chrome('site/style.css')}" />
  </head>

  <body py:match="body" py:attrs="select('@*')">
    <!--! Add site-specific header -->
    <div id="siteheader">
      <!--! Place your header content here... -->
    </div>

    ${select('*|text()')}

    <!--! Add site-specific footer -->
    <div id="sitefooter">
      <!--! Place your footer content here... -->
    </div>
  </body>
</html>