Cannot change background color of twentythirteen theme

Hi, I am trying just to change the background color, but it will not. Is this because of the theme in wordpress that does not allow this. The theme is twentythirteen.
My code is this. Now if I change that background: green; it does not seem to do anything. I have also tried putting !important in front of it, and tried changing it in the dev tools as well.

body {
    background: #f0f0f1;
    color: #3c434a;
    font-family: -apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Oxygen-Sans,Ubuntu,Cantarell,"Helvetica Neue",sans-serif;
    font-size: 13px;
    line-height: 1.4em;
    min-width: 600px;
}

• This topic was modified 3 years, 2 months ago by Yui.
• This topic was modified 3 years, 2 months ago by Yui. Reason: formatting