Alternating post color with nth child

I am looking to alternate the entry background colors. I know how to do this by using:

.hentry:nth-child(2) {
  background-color: #eee;
}

This works however it’s obviously only the post itself. I would like the color to be 100% of the width of the site, not just the background of the post itself.

I can not quite figure out how to do this without changing the whole layout of the post and having it look funny. I have tried a few things but can not really get it working.

I am thinking it is not actually .hentry that I need to do this with, any suggestions?