Modifying the Search Highlighting
You can control search highlighting with an override:
  Formats\WebWorks Help 5.0\Skins\[skin name]\wwhelp_settings.xml
For more information regarding overrides, See “Creating Format Overrides”.
The following markup controls the behavior:
  <Search enable="true">
  <Results showrank="true" />
   <Highlighting enable="true">
    <Colors foreground="#FFFFFF" background="#333399" />
   </Highlighting>
  </Search>
Using an HTML value for the color will help you control the search highlighting color for the text and for the background of the word that is being searched in the output page.
Note: This browser behavior is limited to Internet Explorer.