How do I add a background on welcome page article

Good afternoon everybody,
it might seem easy for you to answer my question but i'm quite desperate now.
How do i add a background color for my article only at the welcome page?
I think it primarily have been in the style.css and I do not know how to remove it.

Like it's in the "small business demo" on http://smthemes.com/demo/smallbusiness/.

I would be very thankful!

cheers

(ref. http://www.vantriel.de)

Hi!
To fix this you can try to edit the file style.css. You just have to add the background for such style element as

.post-1 {
}