Spook,
  I sort of like the blue-ish theme, but you can change thing  Take a look at 
/home/httpd/html/horde/config/pref.php  and you will see a section where you can set the theme.
// UI theme
$_prefs['theme'] = array(
    'value' => 'bluewhite',
    'locked' => false,
    'shared' => true,
    'type' => 'select',
    'desc' => _("Select your color scheme.")
);
Select a theme from the themes directory and set it as the value.  The preloaded themes are here:
/home/httpd/html/horde/
Of course, you will need to make this permanent by creating the appropriate custom-templates.  Let me know if you need a hand with that.