Tablesorter theme, changing line background when button is clicked

I am using tablesorter 2.0, and I am trying to redefine the css theme at the click of a button, but I cannot do anything. I tried adding a little css to the theme file, but I think another attribute overrides it. I want to do change the background color of a string of a specific class .

If anyone can check this out and tell me where to add the class and attribute to this file, this will be appreciated.

Here is the theme file for tablesorter:

table.tablesorter {
    font-family:arial;
    background-color: #CDCDCD;
    margin:10px 0pt 15px;
    font-size: 8pt;
    width: 100%;
    text-align: left;
    border-radius:3px;
}
table.tablesorter thead tr th, table.tablesorter tfoot tr th {
    background-color: #e6EEEE;
    border: 1px solid #FFF;
    font-size: 8pt;
    padding: 4px;
}
table.tablesorter thead tr .header {
    background-image: url(bg.gif);
    background-repeat: no-repeat;
    background-position: center right;
    cursor: pointer;
}
table.tablesorter tbody td {
    color: #3D3D3D;
    padding: 4px;
    background-color: #FFF;
    vertical-align: top;
}
table.tablesorter tbody tr.odd td {
    background-color:#F0F0F6;
}
table.tablesorter thead tr .headerSortUp {
    background-image: url(asc.gif);
}
table.tablesorter thead tr .headerSortDown {
    background-image: url(desc.gif);
}
table.tablesorter thead tr .headerSortDown, table.tablesorter thead tr .headerSortUp {
background-color: #5B5781;
}

Here is the jquery css that I use to change the string (this is the callback from the call to $ .post ()):

function(){
            $("#row_"+id).css("background-color", "orange");
            }