th.asc { background: url('/static/django_tables2/themes/paleblue/img/arrow-active-up.png') no-repeat center left; }
 thead .desc  { text-decoration-color: darkred; background: url('/static/django_tables2/themes/paleblue/img/arrow-active-down.png') no-repeat center left; }

 thead .desc a { color: darkmagenta !important; 
    margin-left: 10px;
 }
 thead .asc a { color: darkmagenta !important; 
    margin-left: 10px;
 }