Many installations have something like: table.wikitable th {background:color;} which would override the background of the sortable header.
background-position: 0% 100%;
}
/* Table Sorting */
-th.headerSort {
+table.sortable th.headerSort {
background-image: url(images/sort_both.gif);
cursor: pointer;
background-repeat: no-repeat;
background-position: center right;
padding-right: 21px;
}
-th.headerSortUp {
+table.sortable th.headerSortUp {
background-image: url(images/sort_up.gif);
}
-th.headerSortDown {
+table.sortable th.headerSortDown {
background-image: url(images/sort_down.gif);
}