Post background color

Hi,
I have createad a different page from the home page and I need to set the background of the post to black.
In the CSS I have:
.ita-post-body
{
padding:10px;
}
which I have created
.ita-post-body2
{
padding:10px;
background-color: #000000;
}
to use in the new page, however, when I go to the new page (php file), I see that this is the part of the code that shows what I have post:

while (have_posts()) {
the_post();
get_template_part('content', 'page');
/* Display comments */
if ( theme_get_option('theme_allow_comments')) {
comments_template();
}

When I go to see the html source code, it generates:

<div class="ita-box ita-post post-10 page type-page status-publish hentry" id="post-10">
	    <div class="ita-box-body ita-post-body">
	            <div class="ita-post-inner ita-article">
	            	                <div class="ita-postcontent">
	                    <!-- article-content -->
	                    <p>HERE'S WHERE MY POST SHOWS UP</p>
	                    <!-- /article-content -->

As you can see, the ita-post-body is on the div, where can I find that so so I can set the backgrond color to black for that class.

Thanks
Regards

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