You can add attibutes to a row, a column or a specific cell with $ct->set_cell_attribute($value,$row,column);
$ct->set_cell_attribute('style="background-color: LightPink;"',2,'');
$ct->set_cell_attribute('style="background-color: LightGreen;"','',2);
$ct->set_cell_attribute('style="background-color: LightBlue;"',10,4);