$objPHPExcel->getActiveSheet()->getComment('E13')->getFillColor()->setRGB('EEEEEE');
в EXCELе это:
ActiveCell.AddComment.Shape.Fill.UserPicture (ImaFile)
$objPHPExcel->getActiveSheet()->getComment('E13')->getFillColor()->setRGB('EEEEEE');
ActiveCell.AddComment.Shape.Fill.UserPicture (ImaFile)