Contact Form Background

I have tried adding the following code into my CSS to make the form background white/opaque, but it does not seem to work. I used the code successfully on another website, but for some reason this time it does not seem to come up.

This is the page where I would like it to be:

http://www.artofpoolcare.com.au/wordpress/pool-cleaning/

I have tried three versions of the code. Ideally I would like this to be a setting for all the pages, not just one page.

—Version A—-
#top.page-id-16 .ajax_form.avia-builder-el-0 {
background: rgba (255, 255, 255, 0.9);
padding: 10px;
}

—Version B—
#top.page-id-16 .ajax_form.avia-builder-el-4 {
background: rgba(255, 255, 255, 0.9);
padding: 10px;
}

—Version C—
.ajax_form.avia-builder-el-4 {
background: rgba(255, 255, 255, 0.9);
padding: 10px;
}

Your help would be greatly appreciated.

Thank you
Ivana