Changing background color Twenty Seventeen

I just installed the Twenty Seventeen theme and I would like to use it. The entire standard website has a white background at the moment, but I would like to have the content on a white background, but on the background (behind that and to the left and right of the content) I would like a different color. I have been looking in the CSS editor, but it’s such a long page of CSS code.

Where can I change the background color?