Add a question class like "header-green" or "header-red" and then add something like this to the end of template.css:
.header-green .question-title-container,
.header-green .questionvalidcontainer {
background-color: #00CC00;
}
.header-red .question-title-container,
.header-red .questionvalidcontainer {
background-color: #FF0000;
}
