The background color of the reply message

I'm having issues changing the color of my message background, I know I've asked questions regarding changing website colors before, however, this time I'm stumped. I've been editing my site in the template.css file like normal but, now, I can't seem to find where this is located in the file! Is it located somewhere different? Am I missing something? If I am missing something then what is it and what is it labeled as in the template.css file? Help!