By default the 'rowStyler' option is invalid for footer rows. To enable it, the datagrid's view should be overridden. Here is the code to make footer rows have 'rowStyler' feature.
var myview = $.extend({}, $.fn.datagrid.defaults.view, {
renderFooter: function(target, container, frozen){
var opts = $.data(target, 'datagrid').options;
var rows = $.data(target, 'datagrid').footer || [];
var fields = $(target).datagrid('getColumnFields', frozen);
var table = ['<table class="datagrid-ftable" cellspacing="0" cellpadding="0" border="0"><tbody>'];
for(var i=0; i<rows.length; i++){
var styleValue = opts.rowStyler ? opts.rowStyler.call(target, i, rows[i]) : '';
var style = styleValue ? 'style="' + styleValue + '"' : '';
table.push('<tr class="datagrid-row" datagrid-row-index="' + i + '"' + style + '>');
table.push(this.renderRow.call(this, target, fields, frozen, i, rows[i]));
table.push('</tr>');
}
table.push('</tbody></table>');
$(container).html(table.join(''));
}
});
$(function(){
$('#dg').datagrid({
view:myview
});
});