In your "stylesheet_original.css" look for the following:
.leftboxheading, .rightboxheading, .centerboxheading, .singleboxheading {
/*background-color: #abbbd3;*/
font-size: 10px;
font-weight: bold;
color: #ffffff;
padding: 3px;
height: 20px;
padding-left: 5px;
}

change the text in red to read: background-color: #008000;

and remember to remove the /* and */