Post Formats and Backgrounds

Hmm, not that I'm aware of. There would have to be some crazy programming that could read the image and set the background color.

I thought so. I saw it on 2 sites, checked the source code and couldn’t figure it out.

http://girlwithacamera.co.uk

https://wordpress.org/themes/ryu/

Looks like they just manually add the CSS for each section:

article.green,
.archive-post.green {
	text-shadow: 0 1px 1px #eef1e6;
	background-color: #d7dec0;
}

article.green img, article.green .wp-caption {
	background: #eef1e6;
}

article.green img:hover,
.archive-post.green img:hover {
	background: #d7dec0;
}

article.orange,
.archive-post.orange {
	text-shadow: 0 1px 1px #ded1c6;
	background-color: #e3c3a9;
}