Content box transparent setting

Hi,

I would like to change the content box back ground to be transparent but only on my home page.

im adding in to the additional CSS the following :

.page-id-156
 #content-box   {
background: rgba(76, 175, 80, 0.3);
}

my style sheet code

#content-box #post-body {
	overflow: hidden;
	background: none repeat scroll 0 0 #ffffff;
	border: 0 solid #DEDEDE;
	box-shadow: 3px 3px 1px rgba(0, 0, 0, 0.05);
	-moz-box-shadow: 3px 3px 1px rgba(0, 0, 0, 0.05);
	-webkit-box-shadow: 3px 3px 1px rgba(0, 0, 0, 0.05);
	margin-bottom: 30px;
	padding: 3%;
	position: relative;
	width: 100%;
	z-index: 0;
}

Please could someone take a look at where im going wrong ?

Thank you in advance

Jphammer